us. nightly news is next. see you back here tonight at 6:00. >> good night, folks. bye-bye. on this friday night, unfit to work. another stunning twist in the air disaster investigation. prosecutors say the co-pilot apparently hid an illness from the airline. torn up doctors notes found in his home. and tonight new scrutiny about how pilots in this country are screened. judgment day once again for amanda knox, the american accused of murdering her roommate. high drama in a late-night ruling in italy. bombshell report. where did fraternity members learn that racist chant caught on camera? and making a difference for a little boy who inspired a movement. why so many people all across the country are wearing yellow today for seth. "nightly news" begins right now. this is "nbc nightly news." reporting tonight from

los angeles, lester holt. good evening. there are still no reasons but there are some intriguing clues out tonight about what could have driven the young co-pilot of germanwings flight 9525 to fly a plane full of people straight into a mountain. we know andreas lubitz was facing health issues. a diagnosis of sufficient concern a doctor noted he shouldn't be working the day of the crash. but like the wreckage that litters the french mountainside, the trail that led to this deadly act remains a series of disconnected pieces. once again we begin in southern france with nbc's bill neely. >> reporter: from his parents' home on a dead end street, and from his own apartment, the things andreas lubitz kept hidden are emerging. torn-up doctors' notes declaring him unfit to work for days, including the day he crashed the plane. notes he should have given to the airline.

"the torn-up sick notes," says the prosecutor "support our assumption that he hid his illness." investigators are now analyzing reports that lubitz suffered from depression. he was examined here exactly two weeks before the crash, but the hospital denied they treated him for depression. his remains lie with those he killed. searchers finding more than 400 body parts, but no body intact. more families of the dead came to a memorial near the site today, a wind-swept place of flowers and the faces of the lost. many relatives angry. >> they are angry. they want to cry. it's a mix of emotions. >> reporter: including pity, felt by the father of one of the three american victims, robert oliver. >> i don't feel anger. i'm really sad for the father -- the parents of that young pilot. >> reporter: police escorted someone from his parents' home today. they've been questioned by french

police. for the families here, the news that the plane's co-pilot had medical problems he may have hidden is no comfort. for them he's simply the man who murdered their loved ones. they are being welcomed here. >> they are home here. they can come when they want. >> reporter: amid the relentless probing of the helicopters and of hundreds of forensic experts, searchers and investigators, the mind of one man and what drove him to commit mass murder remains a mystery. well, investigators from at least four countries including from the fbi are trying to find answers to that. many of them working right here close to the crash site. and there is growing pressure tonight on lubitz's employer, the german airline lufthansa, to reveal exactly what it knew about his mental state. lester? >> all right, bill

neely in france thankfully. -- thankfully the source of things are exceedingly rare. still the shocking turn of events has got people thinking about how pilots in this country are screened and who's looking out for any troubling signs that may arise. nbc's tom costello has our report. >> reporter: if andreas lubitz hid a medical or mental condition from lufthansa, it might have been out of fear that he'd never fly again. [ inaudible ] in 2012 a jetblue pilot suffered a mental breakdown on a flight from las vegas to new york. the co-pilot locked him out of the cockpit, then made an emergency landing. the pilot lost his license. under faa rules updated five years ago, pilots are encouraged to self-report a mental health issue and seek treatment early. usually spending a year out of the cockpit while on disability. but they can return to the cockpit even while taking antidepressants including zoloft, lexapro and prozac if cleared by a doctor.

now working as a counselor. >> the unions and airlines are both telling their pilots it's okay, you know, if you have issues with mental health. make sure you seek help and let us know. >> reporter: but if pilots don't disclose they're on meds and those show up in a random drug test, the pilot could be suspended and fined. while psychological evaluations are not part of the yearly physical, the airlines and unions insist pilots are always under the microscope working with different crews each day. >> you have fellow pilots i've mentioned before that check airmen. the training facility where if pilots have to go in, flight attendants' observations, the corporation itself. so internally there are a lot of mechanisms to try to identify and in a very informal way. >> reporter: but psychologists also say it can be very difficult to know if someone is suffering from a mental health problem without a thorough evaluation. the faa rules are meant to remove the stigma associated with mental illness, but of course that still exists especially for

men reluctant to tell their employer, friends or family that they might need help. but of course for an airline pilot, mistakes could not be higher. lester. >> all right, tom costello, thanks. now to a story that broke late this afternoon. amanda knox will remain a free woman. the american who served nearly four years in an italian prison for the 2007 murder of her roommate has seen her conviction overturned for a second time. along with her former italian boyfriend. nbc's kelly cobiella is in rome. kelly, good evening. >> reporter: lester, good evening. of all the possibilities, legal experts said this was the real long shot that judges would clear amanda knox and raffaele sollecito. tonight the judges said the two did not commit the crime. after more than ten long hours of deliberations late into the night, a stunning decision, the guilty verdict for amanda knox and raffaele sollecito overturned.

sollecito was calm and confident when he left at lunchtime friday. in seattle there were celebrations. >> italy did the right thing. it was the hard decision for the courts, but it was the right decision for raffaele sollecito and amanda knox and meredith kercher's family. her italian lawyer said she was very worried and stressed. it's been seven years and nearly five months since british student meredith kercher was sexually assaulted and stabbed to death in italy. knox and sollecito were convicted of the murder in 2009, acquitted in 2011, then convicted again last year. since her tearful return home after her acquittal, knox seemed to move on with a memoir, a job at a newspaper and last month an engagement. but prison she told matt lauer in 2013,

was always on her mind. >> to lose everything. to lose what i've been able to come back to and rebuild. i think about it all the time. and it's so scary. everything's at stake. >> reporter: in the last few minutes, knox released a statement thanking family and friends and saying, "i'm tremendously relieved and grateful for the decision of the supreme court of italy." one conviction stands for knox, slander for accusing someone else of the crime early in the investigation. lester, the sentence three years time served. >> kelly cobiella in rome tonight. thank you. there is a stunning report out this evening about that racist chant among fraternity members at the university of oklahoma. the video of them singing those awful words set off a firestorm that included students expelled and others disciplined. now we're learning where school investigators say fraternity members first learned that song. we have a report from norman, oklahoma. ♪

>> reporter: ou's president says members of sigma alpha epsilon learned this racist chant at a leadership cruise sponsored by the national fraternity four years ago. >> over time the chant was formalized by the local chapter and was taught to pledges -- >> reporter: david boren said the chant became part of the chapter's institutionalized culture. the report says about a dozen high school students were exposed to the chant on the bus as part of the recruitment activities. >> we can stop it if all of us and the institutions and organizations we belong to and all of us as individuals say we have zero tolerance for racism in america. >> reporter: about two dozen students have been disciplined with community service and cultural sensitivity training. two were expelled. and the chapter has been shut down. levi pettit, a former fraternity member, has publicly apologized. >> a lot of people were hurt not just by those awful words but how they were said. there was laughter on that bus. what were you

thinking? >> i'm not here to talk about what about what happened on the bus. i'm here to apologize for what i did because this is something that i've learned is disgusting and should never happen again in any form. >> reporter: today in a written statement sae confirmed the chant was shared at a past leadership conference but said, "our investigation to date shows no evidence the song was widely shared across the broader organization." >> i would just strongly challenge their nationals and say where are your answers. >> reporter: now the university's president has sent a letter to sae asking for those answers. gabe gutierrez, nbc news, norman, oklahoma. two people are still unaccounted for after an explosion in new york city's east village created an inferno causing three buildings to collapse. at least 25 people were injured including four firefighters and one ems worker. new gas service was being installed at one of the buildings, but it failed inspection shortly before the blast. the longest space

mission ever undertaken by nasa achieved liftoff this afternoon in kazakhstan. on board astronaut scott kelly flashed a thumbs up as he embarks on nearly a full year in orbit. as part of the mission nasa will constantly monitor his vitals and compare them to his genetic mere duplicate on earth, his twin brother mark now an nbc news space and aviation analyst. nbc's peter alexander has more. >> you can see nasa -- >> reporter: with his russian colleagues, astronaut scott kelly is on yet another countdown. this time to do something no other american has ever done, spend an entire year in space. a mission that's already landed him on the cover of "time" magazine. >> care packages -- >> reporter: a lot of attention for soft spoken veteran astronaut who prefers a quiet life in houston. he recently spoke with nbc's tom costello. >> reporter: you will go down as the american astronaut having spent the most time on a space station, setting a record. >> yeah, that's true. what i like to think is records are made to be broken.

>> reporter: but this mission's also unique for who is not along for the ride. >> if he like bumps his head in space, am i going to feel it? unlikely. >> reporter: scott's twin brother, mark, the one with the mustache. himself a former astronaut and the husband of former arizona congresswoman gabby giffords. with mark staying on earth and scott in space, nasa has two guinea pigs for a controlled experiment on the long-term physical effects of space. constantly monitoring the brothers' organ and neurological functions, bone density, muscle tone, vision, hearing and cognitive abilities. critical information for any future mission to mars. >> well, i hope they learn enough to reach further out into the solar system. >> reporter: already scott has spent six months on the station. now a full year in space, leaving behind his girlfriend and two daughters including 20-year-old samantha. there's e-mail, phone calls and skype. but no coming home early. >> god forbid something happens to one of your kids or, you know, somebody else and they're in the hospital, if they're critically

ill, you're not coming back. >> reporter: a full year orbiting 250 miles above the earth, hoping to make another giant leap for mankind. peter alexander, nbc news. there is news tonight of a political shakeup. the long-time leader of the democrats in the senate, minority leader harry reid of nevada, says he will not run for re-election. and there's already a big name making moves to replace him. nbc's kelly o'donnell with details now from washington. >> reporter: the senate's most powerful democrat is stepping out of the ring. >> i'm not going to run for re-election. >> reporter: harry reid, still bruised and partially blinded after a serious home exercise equipment accident in december. >> but this accident has caused us for the first time to have a little down time. >> reporter: aides say around christmas, reid and his wife decided he would not battle for a sixth term. but in january reid

told me despite injuries he was ready to run. and is there any situation related to this that would cause you not to seek re-election? >> no, at this stage i'm fully intending to run. >> reporter: today on nevada radio president obama surprised him with a call. >> he's got that crumb curmudgeonly charm. it's hard to replace. i'm going to miss him. >> reporter: from a childhood in extreme poverty, reid became a scrappy boxer. later a u.s. capital police officer. now 75, grandfather of 19, he will leave this office with a reputation for mastering the tactical side of politics. and that still includes quickly endorsing a successor. democrats are circling around new york's chuck schumer, heading off any knockdown drag-out fight to replace reid in leadership. kelly o'donnell, nbc news, the capitol. a lot more news ahead tonight. why scientists are sounding the alarm about this majestic view in the mountains. an emergency growing by the day here in california. also ahead, the school bus driver being hailed as a hero

tonight, springing into action saving so many young lives.

we're back tonight in los angeles. in a state suffering from an unrelenting drought, california governor jerry brown today signed a $1.1 billion relief package to address the bone-dry conditions. and while that can't make the clouds pour down, rain may not be what the state needs most any way. it might actually need snow more. this is the normal level of snow in california's

mountains, but here is how much there is right now. and our meteorologist dylan dreyer explains why that is such a dire problem. >> reporter: the sierra nevada mountain range is nature's icebox that holds california's precious water supply. but in the last few years that natural reservoir is coming up short. it is absolutely majestic here, and yes, there is snow. but it's so deceptive. the snow pack should be about ten feet higher than it is today. and that has water managers worried. >> this is the absolute lowest snow pack we've recorded on record. >> reporter: rain is important, but why is the snow pack so much more important? >> because it stores the water and then gradually releases it when it's most needed down below in the low lands. this is calmed the airborne snow observatory. >> reporter: nasa is using cutting edge technology including lasers and a spectrometer to measure snow depth in remote locations and

determine how quickly it will melt. >> what we're headed for now is also simply knowing how much water there is in the mountain snow pack. that's something we've never actually known. >> reporter: having this information helps water managers plan for the future. but the current situation is bleak. on the road up to tioga pass these orange markers are unnecessary this year. look at how barren it is. this side of the sierra has absolutely no snow. so why is california in such dire straits? it's all because the jet stream has been diverting the storms. >> it's been too far north and too far off over the ocean. >> reporter: weather patterns that scientists are scrambling to understand. >> there's a real sense of urgency that we need to get a better handle on how to predict them. >> reporter: for now california will have to make due with the water it has as it holds out hope for the future. dylan dreyer, nbc news, tioga pass, california. we are back in just a moment with what the man in charge at apple says he's giving away.

some quick thinking made all the difference in orange county, california when a bus driver hustled all the kids off her school bus moments before the engine erupted in flames. two students were treated at the scene, but thankfully no serious injuries have been reported. take a good look at the duchess of cambridge because this is the last time you'll see her before she becomes a mom for the second time. princess kate wore pink for what was billed as her final public appearance before her due date next month. joining the likes of bill gates, warren buffett and other ultra-wealthy americans, apple's ceo tim cook says he, too, plans to give away his entire fortune to philanthropic causes, after paying for his nephew's college education. cook made the announcement in an interview with "fortune" magazine. his wealth has been estimated at over $800 million. when we come back, you had me at yellow. the little boy whose heartfelt request made him a viral sensation.

making a difference, brought to you by bayer aspirin. take charge of your heart health at iamproheart.com. we're going to end

here tonight with a story of a little boy who can't go into the outside world. so the outside world is coming to him. his simple request has resonated around the globe with so many rooting for him to pass one of the biggest tests anybody could face with flying colors. nbc's joe fryer has tonight's "making a difference" report. >> reporter: like a genie in a lamp, today the internet granted a little boy's simple wish, wear yellow for seth. >> this whole world is wearing yellow just because of you, seth. >> reporter: social media is filled with every shade of yellow you can imagine. a window to the world for a 5-year-old boy in england who can't even leave his hospital room. you see, seth lane was born without an immune system, a rare condition called severe combined immune deficiency. he must live in a sterile environment, a bubble. waiting for the bone marrow transplant that could save his life, he used yellow cue cards to share a request asking everyone to wear his

favorite color today. wish granted. >> hey, seth, i just want to let you know i'm thinking about you today, buddy. i got your back. >> reporter: ashton kutcher answered the call, so did comedian craig ferguson, looking for any excuse to dress like a peek -- a pikachu. from firemen in manchester to a s.w.a.t. team in cleveland, even their dog got the memo. one group in mexico actually took to the air and went sky diving for seth while someone else made a music video. all of it for a little boy hoping to raise awareness about his condition. now the world has a wish for seth, get better soon. >> we love you, seth! >> reporter: joe fryer, nbc news. >> that will do it for us on this friday night. hang in there, seth. i'm lester holt reporting from los angeles for all of us at nbc news, thank you for watching and good night.

if i helped to level the playing field for women and minorities and venture capitals then the battle was worth it. >> right now at 6:00 a defeated ellen powell fighting a silver lining after the jury health her a huge blow. good friday evening. thanks for joining us. i'm janelle wang in for raj mathai. >> i'm jessica agurry. a victory and a defeat for former employee ellen powell. >> the jury deliver add sweeping

rejection of powell's claims of sex discrimination. scott budman has reaction to the verdict but we begin with mark mathews covering the trial since the beginning. he's live in san francisco with more mark? >> reporter: in 40 years of reporting i've never seen anything quite like this. the jury announced they had a verdict. called everybody back to the court at 2:00 this afternoon. everybody lined up. the jury verdict came in, but then as the jurors were polled the judge realized that actually they didn't have the nine votes required on one of the claims that ellen powell was making. he had to send the jury back in to deb liberations for another 25 30 minutes before they finally came back out and delivered a sweeping victory to perkins and a big defeat to ellen powell in her discrimination claim. right after the verdict was delivered, ellen powell left the courtroom and she was followed shortly by the lead attorney for perkins. we'll hear from both of