six degrees warmer for tomorrow. close to 90 on tuesday so get ready. >> more on that in half an hour. nbc's "nightly news" is next. >> see you at 6:00. on this sunday night, new clues? authorities try to verify whether three separate signals may have come from that malaysian jetliner. a sick baby and her family are rescued after their dream journey took a horrible turn. out of control, a spring break party turns violent with more than a hundred arrested and more than a dozen injured. much of it caught on camera. and year of extremes. ann curry takes us around the world to witness up close our changing climate. from nbc news world

headquarters in new york, this is nbc nightly news with lester holt. good evening. australian search coordinators say they are taking seriously what may be underwater signals now picked up by two ships hunting for the black boxes from malaysian air flight 370. officials are warning caution saying it is too early to determine if indeed they are coming from the plane's wreckage especially since they were heard in different parts of the ocean. a third sound was recorded by an australian ship operating more than 300 miles away. in a now month-old search that has seen more than its share of false leads, officials in charge are holding their breath hoping one of those sounds will finally lead them to the ill-fated plane. we start with ian williams. >> reporter: it's dawn now here

in perth and the search is getting under way again with renewed intensity but time is running out for finding the black boxes. in the remote indian ocean, searchers are now chasing two leads to find the black boxes while they're still life in their batteries. a chinese ship has reported it's twice detected a pulse-like frequency, one of the signals lasted for 90 seconds. >> this is an important and encouraging lead, but one which i urge you to continue to treat carefully. >> reporter: experts have questioned the effectiveness of the a hand held sonar device they reportedly used. >> we know you have to be right on top of it. and if it's at depth, 10,000,

12,000 feet you're not going to hear that signal on the surface. >> reporter: tonight a british ship, the hms echo is carrying its own equipment. >> they are trying to vet the information from the chinese. >> reporter: separately today, the towed pinger locator picked up sounds miles from the chinese. they describe the sounds as acoustic events rather than the pulse-like transmissions of a black box. >> there are plenty of other things transmitting at the same frequency. it's a standard underwater frequency. there are about three, and this is one of them. it's not just black box pingers that send the signal out. >> reporter: with numerous false leads on wreckage, it's become a

race against time, even if the batteries last longer. we should receive information from the british ship within the next 24 hours. >> thank you. the majority of the passengers on the plane were chinese, and many of their families had traveled to malaysia to be enclo closer to the investigation. >> reporter: they were waving giant banners and demanding to know where their family members were. most of them have flown back home to beijing because they're not getting the answers out of kuala lumpur they hoped for. they say they'd rather be home where they can be with the rest of the families and provide a united front. as to the latest on the acoustic signals, they are being cautious, not getting their hopes up until they know exactly

what those noises are. they say they've been misled too many times by false leads. they are frustrated. they say they are sad. but more than anything, they say they feel helpless. >> all right. thank you. for more on the sounds that haven about picked up from the search area and the black boxes, we're joined by a former investigator with the ntsb. we heard in the report a few moments ago that at one point the chinese vessel hears this sund for about 90 seconds. is that consistent for what you would be listening for? >> reporter: not really. that is a continuous ping. it's not intermittant of the and when the battery dies, it stops pinging. the pinger is either working or it isn't. you wouldn't have an intermittant signal. the only thing i can think of is if it is ricochetting off something. >> let's assume they find the

black boxes. we understand that the flight recorder has a short memory. it wouldn't tell us what happened in the first part of the flight. but the data recorder, would that at least tell us whether there was human intervention to the point of crash? >> absolutely, lester, because the recorded parameters could give investigators an understanding of whether the auto pilot was actually manipulating the controls and causing the plane to move or if there was human intervention through either the first officer or the captain's control yoke. so you can differentiate that. it is an element on the flight data recorder and so investigators could use that information. now to the long distance rescue mission playing out in the middle of the pacific. today the navy and california international guard rescued a family including their sick baby from a disabled sailboat three days after they sent out a distress call, but their ordeal isn't over yet.

miguel almaguer is monitoring it for us. >> reporter: this is where the family began their journey around the world, a small harbor here in san diego. but they've begun their journey back. a powerful warship equipped for battle is a rescue ship. the 200 man crew plucked the kauffman family from the sea giving much needed aid to their sick little girl, 1-year-old lyra. they plunged out of the plane into the pacific to reach the doomed sailboat and bring them to safety. the kauffmans had long dreamed of sailing the world. >> i think some people like to be all alone, and some people don't. >> reporter: this was their trip of a lifetime, documenting the trip. it started when the rebel heart

departed from san diego for the sea of cortez two years ago. on the latest leg, the family left pour toe vie ar at that six weeks ago. they hit rough waters, losing power and the ability to steer 900 knotical miles off the coast. the boat is crippled. lyra is seriously ill. within hours, a california national guard rescue team boards the boat. 1:00 in the morning, the boat reaches the family. the kauffmans' extended family says just before their journey across the pacific lyra had salmonella poisoning. >> it wasn't something that i thought was a good idea. >> reporter: on social media, there is both support for the family and outrage. many relieved they're safe,

others very critical. tonight the kauffmans are in good hand, but they may be headed home into a sea of controversy. the family and little lyra are all said to be in good condition. as for the rescue, what is said to be a costly one, there's been no discussion as to who will pay for the tab. the military saying right now they are focused on getting this family back on land. authorities in southern california found themselves with a dangerous emergency on their hands when a spring break party involving 15,000 people disintegrated into chaos and violence. it happened in santa barbara. >> reporter: overnight police have used flash grenades, tear gas and rubber bullets to disperse raucous clouds near the isle of vista. >> there's things on fire.

everyone's screaming. all of a sudden, i turn around, people turn around and start being beaten down the street. >> reporter: videos were posted on social media. it took until this morning to restore order. >> all of a sudden we saw a lot of smoke in the air. we couldn't breathe. i know i was choking. >> reporter: authorities say the trouble escalated around 9:30 saturday night when a police officer was hit in the head with a backpack full of bottles. there were more than 100 arrests and at least 44 people were taken to the hospital. among the injured, at least six officers, including one hit in the face with a brick. earlier authorities had gone to a report of a stabbing. they said many of those hospitalized were drunk. a nationwide survey ranked uc santa barbara as the number two top party school. the young sanctioned spring

break party had its own facebook page and draws larn crowds of young people from around the region. many blamed visitors for the problems. thank you out-of-towners for making a mess that we as iv residents have to teal with. what happened tonight is an embarrassment. thanks, tourists. others said it wasn't so simple. if anybody actually believes out-of-towners caused 100% of the damage yesterday, come on, really? as tonight a seaside community cleans up after an unwelcome rite of spring. in detroit tonight, two teenagers are under arrest in connection with a brutal beating of a motorist who stopped to check on a boy after running over the child with his pickup truck. the beating has sparked outrage in that city and beyond. >> reporter: 54 year old steve clings to life in a medically induced coma since last

wednesday. this picture shows his two daughters holding his hand. >> it's hard to see him in the bed laying there not knowing who he is or what's going on. >> reporter: a security camera caught a glimpse of what unfolded. a 10-year-old boy steps into the street, the man hits the boy with his pickup truck, the impact too graphic to show. people respond. what you can't see is that the man stops, gets out of his truck to help. and police say about a dozen bystanders attack and beat him. >> everybody just walks off. >> i don't understand why they were so angry at him. >> if you're that concerned about the kid, why are you jumping all over my dad and jumping in his truck and stealing his belongings. >> reporter: detroit's mayor asked anyone with information to step forward so justice can be

served. it appears the man was not violating any traffic laws. >> the child stepped out in the path of the vehicle. he did try to rent determine aid. >> reporter: the family retains a bed side vigil. >> i pray to god he better make it. they're saying that -- they're saying that they don't know for sure yet. >> reporter: an appeal for justice has raised more than $94,000. there are perhaps 10 suspects still at large while the family hopes their father survives. we're learning more tonight about the events leading to that shooting ram page at ft. hood texas in which three people were killed before the suspect took his open life. our report from nbc's mark potter. ♪ >> reporter: at sunday services near ft. hood, the shooting

victims and their families were in everybody's prayers. >> continue with words of encouragement. continue with prayer. >> reporter: among those feeling very grateful today is theo dus westbrook who feared he had lost his own son in the shooting spree. >> what jonathan? not my jonathan, not my son. >> reporter: his son survived after being wounded in the chest and arm by a gunman identified as specialist ivan lopez. westbrook says he was told that the shooting began at his son's human resource office after lopez got into an argument with others and was told to come back later after requesting a leave of absence form. lopez returned with a hand gun and shot three people there. >> it was like he was saying, okay, buddy, you're next without actually saying that, and my son, you know, is reading all this from the shooter's eyes. then he pulled the trigger and shot my son. >> reporter: a new aerial diagram released by the u.s.

army showed the shooting spree covered a two-block area and involved six buildings. westbrook was shot inside the 49th transportation headquarters. lopez got in his car and fired at others as he drove. after being confronted by a military police officer in a parking lot he then shot and killed himself, leaving behind three dead and 16 wounded. on wednesday, president obama will return to ft. hood for a memorial service. he was also here in 2009 after the shooting massacre then left 13 people dead and more than 30 wounded. lester? >> mark potter. when nightly news continues on this sunday, climate extremes. from more fires to far less ice. ann curry looks at what has become the new normal. and ordinary objects brought together for an extraordinary tribute to the boston bombing

victims.

we're back with an intriguing look at some of the extremes we've been seeing in weather and climate around the world for the last year. ann curry and nbc news have been tracking these changes for a documentary that airs tonight on nbc. >> reporter: jim houston leads the laguna hotshots, an elite group of firefighters on the front lines of some of the most ferocious fires in the country. how have fires changed since you started fighting them? >> it seems that the fire seasons have gone much longer, when i first started it was in a

six month period from june to november. >> reporter: but that has changed dramatically. >> we joke about it being a year-round fire season. >> we can say some general things that we ekt pebt to happen as the planet warms. and one of those is that the southwest will get drier. >> reporter: we have for now a very abnormal situation. >> not abnormal. this is the new normal. >> reporter: and that new normal has sparked a new theory about wildfires, a theory that led us to the top of the world. american glace yol gist has been studying arctic ice for 20 years, and he says the ice is melting at a scale and speed scientists had never imagined possible. he has a surprising new theory about what may be speeding up the warming. >> you can see it's kind of wanting to pull -- >> reporter: the usually pristine ice looks dirty gray in places. >> that is from wildfire soot.

>> reporter: it was hard to imagine, but he was saying that soot from wildfires in north america had traveled all the way here, coating the ice with carbon particles, transforming it into what he calls dark snow. and what happens with dark ice, dark snow? >> light absorbing impurities trap more sunlight and can hasten the melting process. >> reporter: there are more forest fires, and there's going to be more soot. >> yes. >> reporter: climate scientists say we all need to know more about this. ann curry, nbc news, the arctic. >> you can watch the entire documentary right after this broadcast here on nbc. and up next, we'll he show you a former president as you've never seen him before.

this is the 25th year since george h.w. bush became president in 1989.

a sell brace was held at the bush library in texas. jimmy fallon helped put together a little tribute, snippets of the foerm president's speech. >> you can't touch this. my music so hard, thank you for blessing me. >> the former president with little help from the team fallon editing group. and in case you missed it last night, college basketball at its best as the time four became the final two. the u ccon hn ko-co con huskies. when we come back, symbols of strength in boston.

finally tonight, it's been almost a year since the boston marathon bombings and man hunt that left four dead and hundreds injured. and now as the country steels itself to mark the anniversary, a tribute to much of the strength that made boston strong. they are powerful and poignant, symbols of a time of great shock, grief and sadness in

boston. >> it was a time of great mourning here in the city. these objects really are emotion and support and love in material form. >> they are now part of a new exhibit called dear boston which opens tomorrow at the boston library. >> it's items from the memorial that sprung up at copley square. >> it includes hundreds of running shoes, tee shirts, notes and other mementos that were left as tribute to the wounded victims and tribute to the city. the centerpiece, four crosses representing those who died. >> the grief people felt for those four people was an intense part of the memorial. we wanted it to be a place for community. and we want it to be a place for moving forward.

>> the collection also includes heartfelt messages sent from around the world, including this one written on the side of a sneaker. it reads these shoes taught me the joy of running that can never be taken. a powerful message and now a crucial part of boston's history reflecting the strength and solidarity that followed one of its darkest days. >> we bounce back from that. so it will be in our hearts and minds. boston strong lives on, absolutely. >> it gives you pride being from the area. >> the exhibit opens tomorrow and is part of a larger project that is called boston better. that's nbc nightly news for this sunday. brian williams will be here tomorrow. i'm lester holt reporting from new york. from all of us here at nbc news, goodnight.

right now at 6:00, an intense search for a hiker who has been missing for a week. we'll take you live to mt mt. tamalpais. plus -- >> the next thing i know a young naked man is running at me. >> yelling, screaminged a later biting police. a man is under arrest tonight after a crime spree in palo alto. >> more vessels are heading to the indian ocean. what an australian ship confirmed this weekend. >> good evening. i'm diane dwyer. >> and i'm terry mcsweeny. >> happening now dozens of search crews on the ground along with helicopters and planes lookinr