welcome to bbc news, broadcasting to viewers in north america and around the globe. my name is mike embley. our top stories: another deadly shooting in the united states, this one taking place at the headquarters of youtube in northern california. three people were injured by gunfire, one is in a critical condition. the shooter used a handgun and then killed herself. us officials release the list of $50 billion worth of chinese imports that'll be subjected to additional tariffs. and 50 years after the murder of martin luther king, how much progress has america made in tackling racial inequality? at least three people have been wounded in a shooting at youtube headquarters south of san francisco.

police say a woman opened fire with a handgun. she is now dead, apparently of self—inflicted wounds. at least one victim is in critical condition. another person was injured as employees fled into the street. in a moment, we'll get the latest from our reporter in the city of san bruno — but first here's russell trott. the home of one of the world's biggest social media channels, now itself the focus of world attention. police responded to reports of an active shooter at youtube headquarters at just after 12:45pm, as staff gathered for lunch in a patio area of the main building. aerials of the scene in the city of san bruno south of san francisco show officers and security staff apparently frisking for weapons. no—one certain of who was involved or how many and no—one taking any chances. upon arrival, officers encountered numerous people fleeing from the building. it was quite chaotic. we found one victim with an apparent gunshot wound towards the front of the business as we arrived.

several minutes later, while conducting a search of the premises, offices located a second individual with a gunshot wound that appears to have been self—inflicted. a man believed to be the woman shooter's boyfriend is in a critical condition. two other women were also shot before she turned the gun on herself. we are an incredibly tightknit community within youtube and we feel like a family. today it feels like the entire community of youtube and all of the employees were victims of this crime. the injured have been taken to nearby hospitals. it is not known whether the dead gunwoman was a youtube employee. russell trott, bbc news.

our news reporter dave lee is in san bruno. he gave me this update around an hour ago. indeed three people wounded in this attack and one of them critically. as we heard in the piece just before i came on, we understand that the critically injured person, a man, was the boyfriend of the suspect gunwoman, although when asked about that specifically, police said they did not want to talk about motive just yet. they would update us on that and other matters tomorrow. it has been over five hours in this attack took place and youtube‘s headquarters arejust up the road behind me. not all of the employees have yet been able to leave the building to go home because police are obviously treating it as an active crime scene and they are trawling through the area where the attack took base, outside in a courtyard lunch area where employees were having their lunch. they are beginning to get some of those employees out so they can finally go home after what must have been an incredibly long and troubling day.

for their part, youtube said they were incredibly impressed with how law enforcement officers responded. they were on the scene within a few minutes of those initial calls coming in. i think we are still yet to hear more precisely why this attack took place. any more details at all on how the attack developed and how it ended and whether the suspect shootout was a youtube employee? we've not heard any specific detail about the shooter. we do know it's a woman, which is a rarity when it comes to instances like this, particularly in america, involving mass shootings. we don't know whether they are an employee. police wouldn't be drawn on that particular detail. what we do know is that this attack was over quickly.

she have opened fire, wounding three people, taking her own life and by the time police arrived, they arrived at a scene of chaos with people running out of the building, they said, but it did seem that this was the situation made safe relatively quickly. that is all police will tell us at this point. like i say, several media outlets including our partners here, cbs in the us, are saying that law enforcement officials, off the record, saying that one of the critically injured man was the boyfriend of the suspect in the shooting. all coming out on this and we will bring you everything when we get it. —— more. the official list has just been released of chinese imports that the united states plans to subject to new tariffs. they target $50 billion worth of chinese imports. president trump insists chinese intellectual property practices have unfairly harmed american businesses. kim gittleson has more from new york. just two days after china placed tariffs on 128 us products,

the united states has responded with a list of its own. running to 1,300 separate items, the range of chinese imports that could be subject to additional tariffs covers everything from biscuit ovens to flatscreen televisions tojet engines. the us has said that it's specifically focusing on china's robotics, aerospace and machinery sectors. there will now be a 60—day comment period before the list is finalised and the tariffs go into effect. already, several us business groups have said that they oppose the tariffs. kim kallstrom, bbc news, new york. the bbc‘s robin brant in shanghai said china was ready to respond. it says it will respond on an equal level. i think we can expect another list from china's ministry of commerce, a list that will be specific and that it will publish that will show us how it wants to target imports coming here from the united states. what started out as a nascent trade

war, essentially over steel and aluminium dumping has moved on a much more substantial area for the us administration, one where there is much more sympathy as well, about intellectual property, about the chinese government's industrial policy. about the way that us firms and others are treated when they want to invest in china and, more broadly, it is about the inequity many companies say, of the trade relationship between china and the united states. you use the word substantial. many analysts are saying that none of this is enough to change the chinese practices that president trump has attacked so strongly. what is the point of all this? how far do you think it may go? well, look, ithink there are two points. there's the domestic element for the president. there's the candidate, who accused china of raping the united states ofjobs. that's why i think we saw the first move on steel and aluminium.

there's clearly a domestic audience for these measures. this is a president who's trying to show americans and american voters that he's taking action on those election pledges. there is a big issue here about the complaint and most of it is historic. intellectual property, american firms forced to hand over much of their technology. certainly other foreign firms as well. that's been going on for 20 or 30 years. if the chinese were to change that now and there is no change — even if they did, the bad stuff has already happened. there is much more broader sympathy for the president in terms of intellectual property and the inequity of the relationship then there is on, say, steel and aluminium dumping. the relationship between china and the us market access is a huge problem for many american firms. it does seem to be hugely inequitable and it is that that the president is trying to address. the big problem is that you look at that list and it covers

machinery, robotics, aviation, all on the china ‘made in 2020 made in china' list. a big strategic push for china to dominate in those industries, especially in aviation and robotics. all of a sudden, china is not going to abandon a strategic push because of pressure from president trump. let's take a look at some of the other stories making the news. president putin says he's agreed with his turkish counterpart recep tayyip erdogan to speed up the delivery of s—400 air defence missile systems to ankara. the deal has caused alarm amongst turkey's nato partners because the systems cannot be integrated into nato‘s military architecture. in another sign of closer relations, the two presidents earlier launched the construction of a $20 billion nuclear plant. shares in spotify are trading for the first time on the new york stock exchange. they initially went on sale at more than $165 valuing the swedish company

at almost $30 billion. the commonwealth games will officially get underway on australia's gold coast on wednesday. the prince of wales is due to arrive on behalf of the queen and embark on a seven—day tour of the country. he'll be accompanied by the duchess of cornwall and will also tour the athletes‘ village. the prince will hold meetings with australia's prime minister malcolm turnbull, commonwealth leaders attending the sporting tournament and present medals to swimmers. french rail workers have begun three months of rolling strikes, severely disrupting services. fewer than a fifth of trains are running. airline staff, rubbish collectors, and some energy workers have also walked out in protest at president macron‘s planned changes to public services. he also intends to deny new recruits benefits such as guaranteed pay rises and early retirement. lucy williamson reports from paris. to protect their future, france's rail workers are turning to tactics from the past. their right to pay rises, overtime earnt and jobs for life as much a part of national culture

as street protests. at gare du nord, they took their message to the commuters themselves. mr macron, they say, is trying to break the power of the unions, and his government's reforms a first step to privatisation. president macron has promised to transform france and there are many voters who believe reforms are necessary, but these strikers are not appealing to the country's economic head, but to its social heart. france's social model, they say, is what makes us french. it's an argument that's worked before. the test is whether the country will back them. with almost half the rail company's core staff on strike, just i2% of high—speed trains were running today. one in five regional trains. platforms were so crowded that one woman fell onto the tracks at gare du lyon. fellow passengers jumped down to haul her up. translation: i'm really sick and tired of it. they have the right to strike, but not to jeopardise ourjobs. a stand—off with the rail unions may

not do president macron any harm when he's facing competition for right—wing votes, but success may depend on whether public sector workers join the strike. having been elected to change france, mr macron is gambling that france itself has changed. lucy williamson, bbc news, paris. president trump intends to deploy troops to protect the border with mexico until there is a wall and what he called proper security. when they were in office, george w bush and barack 0bama did both send thousands of national guardsmen to the border, but president trump said the entire immigration system needed an overhaul, and accused immigrants of flowing illegally into the us, disappearing and never showing up in court. here's a little of what he's been saying. we have very bad laws for our border and we are going to be doing some things. i've been speaking with general mattis, we will do military things...

until we can have a wall and proper security, we will guide our border with the military. it's a big step. we really have not done that before, certainly not a lot before. however, we will be doing things with mexico and they have to do it otherwise we are not going to do the nafta deal. stay with us on bbc news, still to come: how new technology is being harnessed to monitor some of the world's most endangered species. the accident that happened here was of the sort that can, at worst, produce a meltdown. in this case, the precautions worked, but they didn't work quite well enough to prevent some old fears about the safety features of these stations from resurfacing. the republic of ireland has become the first country in the world

to ban smoking in the workplace. from today, anyone lighting up in offices, businesses, pubs or restaurants will face a heavy fine. the president was on his way out of the washington hilton hotel where he had been addressing a trade union conference. the small crowd outside included his assailant. it has become a symbol of paris. 100 years ago, many parisians wished it had never been built. the eiffel tower's birthday is being marked by a re—enactment of the first ascent by gustave eiffel. this is bbc news. the latest headlines: at least three people have been wounded — one critically — after someone opened fire at the headquarters of youtube in california. the shooter — a woman — is said to have killed herself. us trade officials have published a list of chinese imports worth about $50 billion

that could be targeted it's emerged that british scientists have not been able to confirm the source of the nerve agent used on the former russian spy sergei skripal, and his daughter. the porton down defence research lab has identified it as novichok, and say it's so sophisticated it was most likely state—produced. russia is the only nation known to have made novichok. the government in moscow has said the comments by the head of the lab are "proof" that claims russia was involved are a bluff. the government has concluded that it is highly likely that russia was responsible for the act against sergei skripal and his daughter yulia. theresa may addressing parliament following the attack. the uk government has always blamed russia for the poisoning, an allegation moscow has completely denied. yesterday, the head of the defence research centre at porton down, said the substance used was so sophisticated it was likely only a nationstate

was able to deploy it. but he said that scientists have not verified precisely where it was produced. we are 100% certain that this is from the novichok family of nerve agents. a military grade nerve agent. we provided that information to the police and to the government and that has been our role in this. it is not for us to advise on who made the nerve agent or where it came from. the kremlin has called on theresa may to apologise. however the uk government maintains that russia is behind the poisoning, saying such analysis was only one part of a wider intelligence picture. it is one month since the former spy and his daughter were found unconscious on a bench in salisbury. sergei skripal remains critically ill, his daughter yulia is now conscious and talking. vladimir putin has said he hopes an emergency session of the chemical weapons watchdog in the hague on wednesday will clear russia

of any responsibility. translation: according to the international experts, about 20 countries in the world can produce nerve agents like this. we call for the situation to be studied in every detaile. we have raised at least 20 questions for discussion and i hope this discussion will draw a line under what happened. investigators from the 0pcw visited locations in salisbury following the attack that it the results of their independent test are expected within the week. on wednesday it is 50 years since martin luther king was shot dead on the balcony of the lorrain motel in memphis, tennessee. equality under the law was achieved, on paper, with the passing of the civil rights act, but dr king's dream of full racial equality is unfulfilled. african—americans face higher rates of poverty, unemployment, police violence, and incarceration. clive myrie has been finding out more in america's most segregated city, milwaukee.

martin luther king said there were two americas. one was white, overflowing with the milk of prosperity. the other, black, a lonely island of poverty and brutality. 50 years after his death, are those two americas any closer to being reconciled ? 0n the face of it, little has changed at the martin luther king elementary school in the midwestern city of milwaukee. 98% of the pupils are black, reflecting the demographic of the local area. so while segregation is now illegal in education, it happens anyway. with liberty and justice for all... fine words, but milwaukee is the most segregated city in america, where there isn't liberty and justice for all. the north and west are mainly black, the south and east, mainly white, and in the affluent suburbs, postal workers are the most

frequent black visitors. academic marc levine has written extensively about the racial divide here. milwaukee, in terms of the level of segregation in the town, is precisely the same as it was 50 years ago. a black household making $100,000 a year has a 20 times greater possibility of living in a concentrated poverty neighbourhood than a white family. and it's notjust in housing that america remains a land divided, half a century after dr king had a dream. 50 years ago, the unemployment rate was 6.7%. in 2017, 7.5%. still roughly twice the rate of whites. and 50 years ago, just over 40% of black people owned homes, about the same rate as today, yet 70% of whites are home owners. now they're taking everything we had but we are not afraid of them, no more.

housing has always been a racial faultline america. black people have sought and been denied the right to live where they want or refused loans for homes. in 1967, thousands marched for fairness in milwaukee. singing these people were some of the protestors. demonstrating on this bridge, the divide between black and white in the city. the white people with their children and everybody else, their bricks and bottles, name—calling. there was all kinds of things that happened by the time you got to the end of that bridge. 0ld newsreels help jog memories of their sacrifice. that's my mother! that's your mother there? yes. yes, that's my dear mother. but how much do they think things have changed in america? milwaukee has become more tolerant in where they place the blacks,

but they're still doing the same thing, they're segregating us, putting us into different areas though. i don't care how much money you've got, what you got, they're looking at this. right. but some are fighting back. a non—profit organisation, the milwaukee fair housing council, has undercover researchers who investigate landlords over racism. i met two of the researchers, one black, one white, who went to the same landlord looking for a flat. they were very, very accommodating to me. they were keen? oh, yeah. yeah, yeah. i was told to come back later. i subsequently went back about a week later and was told nothing was available. that was it? that was it. it's really disheartening because it is a symptom of something for me that is really sick in this society. no matter what i've accomplished, no matter what my station in life, i'm reminded that i'm a black person living in america.

dr king wanted these children to achieve their american dream, and he wanted this country to find its soul. while the level of inequality remains, he remains a voice of anguish for millions. conservationists are trying out new ways to monitor endangered species. they're borrowing techniques from astronomers to identify animals automatically, from their heat signature. 0ur science correspondent pallab ghosh has the details. the heat signature of a group of chimps wandering through their habitat. this is a new way of keeping track of endangered species. a little further along, rhinos snuffling the ground for food. and these baboons can be seen even through the tree tops. currently conservationists such as serge wich count the animals from the ground. it's a painstaking process and not always accurate. we have too many areas

where we don't know how many animals there are. we don't know where they are. and we don't know if those populations are increasing or decreasing, and that's a real problem for conservation management. here at knowsley safari park in merseyside, serge is testing out a system which films the animals heat signature from the air. the drone can spot far more animals from the air, but the problem was that the researchers could not tell what they were, especially if they were far away. what they needed was a system that could identify them from the heat they gave off. what serge needed was the help of an astronomer. claire burke uses software which automatically identifies the size and age of stars from the pattern of heat they give off. she adapted it to analyse pictures from serge's drone, and she found that different animals have their own distinct heat pattern. each different species of animal has a unique thermal fingerprint. so they all look different depending on what species they are. and because of this we can construct a machine learning —based algorithm which will tell the difference automatically between rhinos

and elephants and giraffes and this is what we hope to do with it at the end of the day. the researchers have found that there drone system can successfully identify species at knowsley safari park. so they will be trying it out in the wild next month. if it performs just as well, it will give conservationists the detailed information they need to protect the planets endangered animals. pallab ghosh, bbc news, liverpool. the duke of edinburgh — who's 96 — has been admitted to hospital in central london for a hip operation. in a statement, buckingham palace said the procedure had been planned and would take place on wednesday at the king edward vii hospital in london. the duke has missed several recent royal events rupert murdoch's 21st century fox has proposed legally separating sky news from the wider group or selling it to a rival such as disney. fox wants to buy the remaining stake of sky it does not currently

own but the regulator has concerns about media independence. a reminder of our top story. police in california say the suspected attacker in a shooting at youtube headquarters in the city of san bruno, south of san francisco, is dead. the woman, who used a handgun, seems to have shot herself. three other people are being treated in hospital; one is in critical condition. there are unconfirmed reports that the most seriously wounded person is a former partner of the shooter. police said all buildings are how secure. senior staff at you tube have officially thanked the authorities and employees for their help. news of the shooting first emerged on social media with staff tweeting that they had heard shots and were in lockdown. more on our website. well, wednesday is going to be one

of those days where you might look at the sky and just think the weather cannot make its mind up. it's really going to be that changeable from hour to hour. we'll have strong sunshine and downpours as well. some of them will bring thunder, possibly hail and some gusty winds as well. it's all thanks to this area of low pressure. you can see the clouds spinning around here, that's been sitting to the south—west of the british isles over the last couple of days, and finally, that low will be barrelling across the uk. so into the early hours of wednesday morning, already some showers around across a number of western and south—western areas and still, we have the cold air across scotland. in the last few days, throughout easter, we have snow across the northern parts of the uk. we still have the remnants of that cold weather in scotland and it's still with us on wednesday. but to the south, here's that showery low that will be moving across the uk.

so the thinking is that first thing in the morning, some of us will have showers, others will have clear blue skies. it'll already be very mixed first thing in the morning. but let's zoom into scotland first of all because here, we still have the snow. it will be falling mostly across the hills and mountains but in the lowlands, i suppose, there is a chance of some sleet falling here. but to the south, across england and wales, not necessarily northern ireland, but england and wales, lots of showers around. but you can see, it's sort of like peppering england and wales. so very hit and miss. there is a chance that some of us will miss the showers altogether, whereas others might get lots of them. and then you've got the hail and thunder which i mentioned earlier on. now, eventually into thursday, that showery low moves out into scandinavia. you can see here it is, just approaching denmark. we're in between weather systems, and actually a chilly start to thursday. chilly, i think a frost in one of two areas. that's why the temperatures will be a little bit lower on thursday, 10—12 degrees, but then we've got a change on the way for thursday into friday. this low pressure comes in.

so this is another area of weather, cloud and rain out west here. but the winds are blowing out of the south. given some sunshine, we're thinking maybe eastern areas, it is going to warm up again. so possibly getting up to around about 15 or 16 degrees on friday. whereas in the west, where you have the cloud and rain, of course, it's going to be quite a bit cooler. maybe 10 degrees in belfast. towards the end of the week, friday, saturday quite possibly as well, we're still hanging onto some of the milder weather across south—eastern areas. so very changeable weather, i think, over the next few days, but it will improve eventually. this is bbc news, the headlines: police in california say the suspected attacker in a shooting at youtube headquarters in san bruno, south of san francisco, is dead. they believe she shot herself. the attacker used a handgun. three people are being treated in hospital, one, thought to be a former partner of the attacker, is in critical condition.

american trade officials have published a list of chinese imports worth about $50 billion that could be targeted by additional tariffs, the latest move in president donald trump's trade confrontation with beijing. the list covers more than 1,300 items. it's emerged that british scientists have not been able to confirm the source of the nerve agent used on the former russian spy sergei skripal and his daughter. they have identified it as novichok and say it's so sophisticated it was most likely state—produced. russia is the only nation known to have made novichok. now on bbc news, hardtalk.