welcome to bbc news — i'm lewis vaughanjones — our top stories: a police officer dies after being rammed by a car outside the us capitol building in washington — another officer is being treated in hospital. the suspect who emerged from the car with a knife and ran at officers was shot — and died in hospital. the top homicide investigator for the us city of minneapolis gives evidence on day five of the trial into the alleged murder of george floyd. remaining calm under the pressure — the life—saving operation that took place while a fire was raging. and — a different big bang — new research suggests the asteroid that killed off the dinosaurs may have helped create the rainforests.

a police officer has died and another is in hospital after an attack on the us capitol. a man carrying a knife rammed a car into a barricade, before he was shot dead by police. president biden said he was heartbroken over the death of the officer. it's the second time the capitol has been targeted this year, after supporters of donald trump stormed the building in january. here's our north america editorjon sopel. sirens wail. here's our north america editorjon sopel. sirens wail. we've been here before. lunchtime on a cold easter day and another emergency at the capitol. sirens wail. a man in a blue car rams two us

capitol police officers near a barrier. as he gets out of his vehicle, knife in hand, he's shot and has now died. immediately, congress goes into lockdown. a helicopter�*s summoned and lands in front of the capitol building. and the national guard, which has been on duty since the capitol riots ofjanuary 6, is mobilised. another terrifying moment for those who work in the congressional offices. at a hastily organised news conference, confirmation that one of the police officers has died as well. and it is with a very, very heavy heart that i announce one of our officers has succumbed to his injuries. but the assailant doesn't seem to have been on anyone�*s radar screens, and police are saying there doesn't seem to be an ongoing threat.

it does not appear that he is known to the capitol police or the metropolitan police department at this time. crosstalk. sir? is this a terrorism—related incident? _ it does not appear to be terrorism—related, but obviously, we'll continue to investigate to see if there's some type of nexus along those lines. it was only a few days ago that some of the intense security around the capitol, following january's shocking assault, was eased. just a week ago, the driver wouldn't have been able to get as close to the building as he did. what's happened today may be totally unrelated to the events of january 6, but there's a terrible sense of deja vu, a further heightening of the feeling of vulnerability. and once again, above america's august and imposing capitol building, flags have been ordered to fly at half—staff. jon sopel, bbc news, at the capitol. barbara plett usher, our us state department correspondent is outside the us capitol. over the past weeks, i think the city had begun to relax a bit more because since january 6,

there'd been a massive security increase around the capitol building, as you know. there had been some warnings about possible attacks, but nothing had happened. and now something has, so people are on edge again and nervous about what to expect. now, this is nothing like on the scale, of course, of what happened onjanuary 6 — which was a mob storming the capitol building with arms, hunting down congresspeople, attacking police officers. this is — seems to be a one—man attack. at this point, it appears that he acted alone. it's also not at all clear that he might be, you know, connected to some kind of political or other cause. the officers who spoke to us earlier said that they were not calling it a terrorist attack and this man has not appeared on law enforcement radar before, he's not known to police, so it's not clear what his motivation was. that will obviously be a big part of the investigation but, yes, it has rattled people to come three months afterjanuary 6, and some of the congressional aides that the bbc spoke to said that did make them nervous, especially with the security around, that another attack could happen.

well earlier i spoke to tracy walder who's a former cia officer and fbi special agent. i asked him what he thought investigators will be focussed on. we can now speak to tracy walder who's a former cia so one of the things i do think they will be looking at is clearly emotive. the suspect�*s name is noah greene and it has since sort of come out through his social media that he had ties to the nation of islam which, through our southern poverty law center here in the united states, is listed as a known hate group. so i think they will be looking at that in terms of motive and i think they will also be sort of broadening out their reach in terms

of who they are going to look at, what kind of lists they are going to start putting on — people on. i think sometimes we brand terror as looking some way or believing a certain ideology and i think perhaps this is a wake—up call that it sort of comes in all different shapes and sizes. yeah, we should just obviously stress some of the details you mentioned there are not yet official, from official sources. correct. let's take a look at — we're looking at pictures just as you speak there of the incident, of the car and how close — orfar away, given your perspective — it got to the capitol building. what do you make of the level of security around the building right now? so i'm a bit surprised. it looks like it came through the north constitution entrance, barricaded section. from what i understand, sections had been removed and he was able to get — in my professional opinion —

a little too close for my comfort. but i think that it's difficult here in america, would have accepted the level of security that we currently have now at airports and i'm not sure that they would have accepted sort of a larger perimeter. as you have mentioned before, there were calls to, you know, take down the barricades, take the fences, send home the national guard and so, i think our tolerance here for fortifying things and for enhanced security is sometimes quite low and i do think that there needed to be a larger perimeter, i do think he was able to get a little bit too close for my comfort. well, that's really interesting and it feeds into my last question, really, which is about the symbolism, i suppose, of this — you know, this incident in itself, just the location and the timing means it hits people right across america very acutely. so, ithink, you know, that is the cradle of our democracy, right?

capitol hill is something that i would say most people over the world really associate with america and with our sense of freedom and democracy. and when you have someone that specifically goes after those sort of landmarks, in my opinion, they're trying to make a statement — again, we don't know what the motive is — but to select that, our capitol building really is making a statement to the american people that perhaps their democracy is not safe and perhaps the people that they elected to enhance that democracy are not safe, either, and that can be very unsettling. a minneapolis homicide investigator has said police officer, derek chauvin, used "totally unnecessary" deadly force when kneeling on george floyd's neck during an arrest last may. he was giving evidence on day five of the trial of mr chauvin, the white, former officer, accused of killing mr floyd. here's a bit of what lieutenant richard zimmerman had to say, responding to questions from the prosecution.

what is your, you know, your view of that use of force during that time period? totally unnecessary. what do you mean? well, first of all, pulling him down to the ground facedown and putting your knee on a neck for that amount of — that amount of time, isjust uncalled for. i saw no reason why the officers felt they were in danger, if that's what they felt. and that's what they would have to have felt to be able to use that kind of force. our correspondent, lebo diseko, is in minneapolis and has been watching the trial. today has been very much about the police response. lt zimmerman, one of the longest—serving and most respected officers here in minneapolis, telling the court that in his 35 years on this force in minneapolis, he has never been trained

to kneel on someone�*s neck and that is because it constitutes deadly force. also talking about the fact that once somebody is in handcuffs, they no longer constitute the same level of threat. and really saying that as a police officer, you have a duty of care to somebody once they are handcuffed, that their safety is your responsibility. major league baseball has announced it's moving its all—star game out of atlanta following the state of georgia's adoption of a new law that affects the right to vote. critics of the new legislation claim it makes it harder for black people and other minorities to vote in elections. the announcement comes a day after president biden called for the game — which was set to be at the home of the atlanta braves — to be rescheduled. the sport's commissioner said baseball supported voting rights for all americans.

let's get some of the day's other news. taiwanese prosecutors have sought an arrest warrant for a construction site manager whose truck is suspected of causing a train accident in which at least 50 people died. the train hit the lorry that slid onto the tracks from the building site causing hundreds of people to be trapped for hours. the train was packed with local tourists travelling to celebrate a local holiday and is the island's worst railway disaster in decades. officials from tehran and washington will travel to vienna next week, as part of efforts with other world powers to revive the 2015 iranian nuclear deal. the us and iran are not expected to hold direct talks. but russia has said the talks are on the right track. the iran nuclear deal was scrapped by president trump's administration, after he accused tehran of breaking the conditions.

india's cricket legend, sachin tendulkar, has been hospitalised after testing positive to coronavirus earlier this week. the former captain said he had decided to go to a hospital in mumbai �*as a matter of abundant precaution under medical advice�*, and he added that he was hoping to be back new research suggests the asteroid impact that killed off the dinosaurs also gave birth to our planet's tropical rainforests as we know them. paleo—biologist, dr monica carvalho from the smithsonian tropical research institute is one of those researchers and joined me to explain the study. we found that after the impact or with the impact, 45% of tropical species disappeared, and it took about 8 million years for diversity to recover. crosstalk. 8 million years is obviously a huge expanse of time, and when it did come back,

what was different? forests were very different. so forests that came back resemble a lot rainforests that we know today, they were dominated by flowering plants, they were very dense and they had the same levels of intense ecological interaction that we see today. in the age of dinosaurs, that was not the case. the dominant plants were not flowering plants, it was a mixture of ferns, conifers and flowering plants, and it was actually a pretty widely open rainforest back then. and why the difference, why the change do you think when it came back finally after all those millions of years? that is the key question. so... not exactly sure, we think that it could be a mixture of factors, it could be that in the past dinosaurs actually helped keeping the forest open, something very similar to what happened in the african savanna with large elephants knocking down trees,

it could be that there was a selective extinction against conifers in the tropics during the extinction event, or it could be that the asteroid's impact, all the ash and the vaporised rock and dust that was thrown out into the sky, fell down again and acted kind of as a fertiliser, that enabled flowering plants to actually take over. that is really interesting and is there anything we can take from what happened and apply it to today? this is an example of a global ecological catastrophe,

and even though it was really fast, it is something that we can relate, or it is an analogue to the rate at which we are destroying natural ecosystems today, and kind of tweaking the global climate. so the bottom line is that once rainforests go out, they will not come back. something different will come back and it will take millions of years for that. this is bbc news, the latest headlines: police guarding the capitol building in washington have shot and killed a man who drove his car into two police officers. one of the officers has died. a minneapolis homicide investigator has said police officer derek chauvin used "totally unnecessary" deadly force when kneeling on george floyd's neck during an arrest last may. the netherlands is suspending the use of the astrazeneca coronavirus vaccine for people under the age of 60, as a precautionary measure. it follows five reports of cases of blood clots in women who'd been vaccinated, out of a total of 400,000 people who've been given the jab. one of the women died. germany took a similar step on tuesday. meanwhile the uk's medical regulator revealed there have been 30 cases of rare blood

clotting in people who've had the oxford—astrazeneca jab and seven people have died. that's out of a total of 18 million administered doses in the uk. our science correspondent rebecca morelle explains more. these clots are unusual in that they're associated with low platelet levels, and platelets are a type of blood cell that normally cause bleeding, not clotting, and these clots can affect the brain, too. so, what needs to be unpicked is whether these are happening naturally or whether they're a really rare reaction to the astrazeneca jab. the incidence is low, so 30 cases out of 18 million jobs. so that's about one event in every 600,000 astrazeneca vaccines. and the uk regulator said there have been two cases of brain blood clots with the pfizer vaccine, too, but these don't have the low platelet counts associated with them, so they're slightly different. but these clots have caused some countries to actually restrict who they give

the vaccine to. so, today, the netherlands has announced that it's not going to be giving the astrazeneca jab to people under the age of 60. germany are doing the same thing, too, but the uk is continuing with its vaccine roll—out. and the uk regulator stresses, along with the european medicines agency and the world health organization, that the benefits of having a vaccination and the protection that they offer from coronavirus far, far outweigh any potential risk. so, their message is, if you are offered the vaccination, to go ahead and take up that offer. russian state media have released a series of videos apparently intended to discredit the jailed opposition figure alexei navalny. two days after the critic of president putin declared a hunger strike, pro—kremlin media published without a limp to dispute claims mr navalny is suffering from leg and back pain. mr navalny began his hunger strike saying he'd been refused access to a civilian doctor, and that the russian

penal colony is a torture facility. still in russia, a medical team has successfully completed open heart surgery on a patient, as firefighters battled to control a serious fire at a hospital in the far east of the country. the leader of the heart unit said his team had to do everything to save their patient. gareth barlow reports. as smoke billowed out of the building, firefighters rushed in. emergency services scrambled to evacuate more than 120 patients being treated at the tsarist—era hospital. amid the chaos, one team of medics valiantly carried on. eight doctors and nurses performed a two—hour open heart operation. with electricity cut by the fire, an emergency power cable was fed into the building to keep vital life—support systems operational.

translation: when smoke came in, we installed special— electric fire brigade fans to evacuate the smoke from the first floor and from the operation room. the operation was a success, and the patient safely transferred to another unit. no one was injured by the fire. however, the impact of the blaze will be keenly felt, as the hospital is the only in the region with a specialist heart unit. to new york now, where the city's famous broadway theatres, art and entertainment venues are beginning to reopen at limited capacity. theatres have been empty as the city battled against the covid pandemic, but from friday, theatres are allowed to reopen at 33% capacity. new york city's mayor, bill de blasio, says he's keen to get theatres back up and running again, with a full reopening by 2021.

——the end of 2021. kelsey lu is a cellist in "this is not a test", performed at the shed threatre, one of the first three venues in new york to reopen this weekend. theyjoin me now. thank you for coming on the programme. thank you for coming on the programme-— thank you for coming on the rouramme. ., ~ i. ., ., programme. thank you for having me. are programme. thank you for having me- are you _ programme. thank you for having me. are you looking _ programme. thank you for having me. are you looking forward - programme. thank you for having me. are you looking forward to i me. are you looking forward to performing _ me. are you looking forward to performing again? _ me. are you looking forward to performing again? oh - me. are you looking forward to performing again? oh my- me. are you looking forward to | performing again? oh my gosh, that is an understatement. - performing again? oh my gosh, that is an understatement. i- that is an understatement. i never knew that i would be as excited to perform again as much as i am now in this lifetime. much as i am now in this lifetime-— much as i am now in this lifetime. �* , ., lifetime. any nerves at all, not about _ lifetime. any nerves at all, not about the _ lifetime. any nerves at all, not about the performing l not about the performing because i am sure you are not nervous about that, but the limited audience and the procedures that everyone has to go through to get the performance up and running? i performance up and running? i think that at this point we are all pretty used to having rules and regulations, buti all pretty used to having rules and regulations, but i think what really matters is the music, and that is what shines

through and the energy that is in the room, and everyonejust being excited to perform again, and to see music and to feel it, and experience, experience something that we have all missed for so long. and so yeah, that probably is going to be a little jarring, but once it all starts, that will dissipate and fade away. and how has this _ dissipate and fade away. and how has this period - dissipate and fade away. and how has this period been for you, i am how has this period been for you, iam presuming how has this period been for you, i am presuming the longest period without playing and performing in your career? yeah, it has been honestly incredibly depressing, i mean at first it started out pretty nice, because i hadn't had so much time to myself, and not being on the road and touring and ifelt this new being on the road and touring and i felt this new surge of energy and inspiration, and then the loneliness and everything that, i don't know, time that i was faced with,

that performance is such a huge part of living and thriving for me, it is my lifeline, and having that exchange of energy between audience and... people, and it really started to affect me, and my mental state, so i was yeah, it was really, really hard. i was yeah, it was really, really hard. , ., ., , , hard. i 'ust want to pick up, the hard. i just want to pick up, the importance _ hard. i just want to pick up, the importance of— hard. ijust want to pick up, i the importance of performing hard. ijust want to pick up, - the importance of performing to that audience for you and your mental health, and it is going to be strange, not going to back to what it was before, this is not thousands of people, this is a much smaller number, that affect how you approach the performance? ida. approach the performance? no, not at all- _ approach the performance? no, not at all- i— approach the performance? no, not at all. i mean _ approach the performance? no, not at all. i mean that _ approach the performance? iirr, not at all. i mean that is how i started performing, not at all. i mean that is how istarted performing, i not at all. i mean that is how i started performing, i didn't start performing for thousands of people, i started performing for a few people, i started performing for small groups and intimate settings, and i love intimate settings, and i love intimate settings. i think that

is a special thing, and so i think also in that case, you are able to maybe even connect with people on a deeper level. so no, i don't think that would affect anything at all.- affect anything at all. kelsey lu, thank — affect anything at all. kelsey lu, thank you, _ affect anything at all. kelsey lu, thank you, hope - affect anything at all. kelsey lu, thank you, hope you - affect anything at all. kelsey i lu, thank you, hope you enjoy the performances when you get back out there. all around the world, despite the global pandemic, millions of people will be marking the easter holiday. it is of course one of the most important dates in the christian calendar, but plenty of non—believers will be celebrating too. for them it's more about confection than resurrection, as the bbc�*s tim allman explains. the easter bunny gets everywhere these days. here he is underwater, off the florida keys. well, actually, this is captain spencer slate, a local scuba—diving operator. he is setting up

a somewhat elaborate it is all in a good cause, raising money for local children in need. and in case you're wondering, all the eggs have non—toxic colouring and are environmentally friendly. speaking of eggs, take a look at these. in hungary, there is a long easter tradition of decorating them, intricate designs, delicate paintwork. little oval works of art. translation: over 30 years i have got to know the egg i as a material to work with. it may be very thin but it is still malleable. so we know each other, the egg and i, me and the egg. these eggs at london zoo are not quite as impressive but they do theirjob. every year, treats are hidden away by the keepers and the monkeys go looking for them. and notjust the monkeys — the meerkats also like to get involved.

across the other side of the world, a similar story at this park in new south wales. the local wildlife getting into the swing of things. although this koala still prefers eucalyptus leaves to easter eggs. before i go, here are some pictures of the tokyo 2020 olympic torch making it's way through the nagano prefecture in central japan. it is called 2020 tokyo, of course, though it is taking place in 2021. the torch would normally then be carried to the more western city of osaka, but authorities may cancel that leg of the relay, due to the region's covid restrictions. the 121—day relay is seen as the first major test of olympic organisers' ability to hold a large event under strict coronavirus curbs.

you can reach me on twitter, i'm @lvaughanjones. this is bbc news. hello there. it's likely to be a dry day for most of the united kingdom today, but there will be contrasts. where we keep the cloud as we had yesterday, temperatures will be held into high single figures, but in the sunshine, potentially 14—15. now, under the starry skies, that's where we see the frost as we start this saturday morning, but you can see the thicker cloud across northern scotland, central and eastern england, perhaps east wales. and there could also be a little bit of mist and fog where we've kept the clear skies as well. but the day is likely to give us quite a bit of cloud across central and eastern areas. it's likely to lift a little as we go through the day and the skies brighten. similarly so across northern scotland, we keep quite a bit. for the likes of lincolnshire, east anglia and the south east, though, it could remain overcast all day.

and with that keen breeze still quite gusty through the channel, only eights and nines, but 13—15 in the sunnier spells. now, as we go through the evening and overnight, we tend to thicken our cloud in the north, but under the starry skies elsewhere, again we can expect a touch of frost. but you may have noticed the approach of some rain for the north of scotland, and that's the start of the transition to much colder air. it's this particular weather front here, as you can see, and behind it, there's arctic air following. so, we are going to have another blast of cold air as we head through in towards easter monday, but for sunday, easter day, a little bit of mist and fog around. actually, we should see a bit more sunshine for england and wales, but cloudier skies with rain for scotland followed by snow and cloudier skies for northern ireland. eventually, we'll see some of that wet weather coming in through the afternoon. but notice the temperatures. we've lost that keen north—easterly. they're a little bit higher temporarily. but overnight sunday into monday, that weather front introduces that colder air right the way across the uk, an arctic blast for all of us. and notjust the cold air, but a strong to gale—force

north wind, as well, which will accentuate the chill. clearly, the showers are quite prevalent for northern scotland, but they may well work their way down through the irish sea, down the east coast of both england and scotland as well. but there should be some sunshine between, but itjust will feel much colder, more like winter. these are the temperatures on the thermometer, but you add on that wind—chill, and it will feel significantly colder. so, big changes afoot, and that may well last into the start of the new week into tuesday, as well, as you can see. as ever, you can keep up to date on the weather on the website. that's where all the warnings are. bye— bye.

this is bbc news —

the headlines: a police officer has been killed in an attack near the us capitol building in washington after a man drove his car into two officers — before getting out of the vehicle and lunging at them with a knife. the man was then shot by police. he later died. a minneapolis homicide investigator has said police officer, derek chauvin, used "totally unnecessary" deadly force when kneeling on george floyd's neck during an arrest last may. mr chauvin denies the charges against him. taiwanese prosecutors have sought an arrest warrant for a construction site manager whose truck is suspected of causing a train accident in which at least 50 people died. the train hit the lorry that slid onto the tracks from the building site causing hundreds of people to be trapped.