in a matter of seconds, the bridge collapsing in a mass of twisted metal. moments before the collision, the ship issuing a mayday. authorities stopping traffic with just seconds to spare. tonight my conversations with the mayor and governor and witnesses who captured some of the stunning images. what do you think when you look at the video now? >> i still in shock, definitely in disbelief. >> now that urgent search. a construction crew filling potholes in the bridge now missing. two found alive, but six unaccounted for. the all-out effort by sea and by air, and the questions, why did the ship lose control? and how could it happen in one of the country's biggest ports? our full coverage ahead. also tonight, the high-stakes battle at the supreme court over the abortion pill. the major case that could restrict access, including through the mail. what the justices signaled today. the new details and what was found in the federal raids on the homes of sean "diddy" combs, and his attorney firing back tonight. >> announcer: this is "nbc nightly news" with lester holt, reporting tonight from baltimore. >> good evening, everyone, from baltimore. it was described as a cathedral of american infrastructure. tonight the francis scott key bridge is a mangled ruin, and there is an urgent search under way for six people missing after a huge container ship on its way out of baltimore harbor rammed a pillar in the dark of night. daylight revealing the twisted wreckage pinning the ship below. two people were rescued, but six missing roadworkers are now feared dead, according to their construction company. officials say a mayday call from the ship just before impact gave officials just enough time to stop traffic and prevent more cars and people from falling into the water. thousands of people traverse this bridge every day, and though president biden is vowing to rebuild, it could take months after a disaster no one saw coming. tonight rescue teams with sonar equipment urgently searching frigid waters near baltimore's collapsed francis scott key bridge. >> this is very much still a search-and-rescue mission. we're still actively looking for survivors. >> reporter: what remains of that structure now piles of twisted metal atop of a container ship after a nightmare unfolded early this morning. >> the whole bridge just fell down. >> reporter: a camera was recording around 1:30 a.m. you can see cars crossing the bridge as a ship called the "dali," with smoke pouring out of it, gets dangerously close to one of the bridge's pillars and then hits it, sending the massive bridge tumbling into the water. >> be advised the entire bridge, the entire key bridge is in the harbor. >> reporter: officials say an eight-person construction crew was on the bridge fixing potholes. you can see lights blinking from their parked vehicles before the roadway crumbled. rescuers found two survivors. authorities say six people are missing. the construction company told nbc news they are presumed dead. >> yo, what the [ bleep ]! >> reporter: toby gutermuth had just gotten off work and captured this stunning video. >> i saw what i thought was cargo falling off the front of the ship, causing some splashing. so i started recording. >> what do you think when you look at the video now? >> i still am in shock, definitely, in disbelief. >> can't believe that happened, you know. >> toby and his friend christian miller telling me they narrowly escaped the disaster. you had gone across that bridge? >> oh, yeah, we had gone across the bridge. >> within? >> within 30 minutes, roughly. >> of the accident? >> yep. >> and were ready to go back any minute. >> what did it sound like, the impact? >> you could hear scraping, metal debris, debris hitting the water. >> and tonight we're learning about remarkable efforts that likely saved lives. video shows two cars crossing the bridge about 30 seconds before the bridge fell. the ship had sent a mayday signal before the collision, allowing authorities to stop any other vehicles from going across. >> i need one of you guys on the south side, one of you guys on the north side, hold all traffic on the key bridge. there is a ship approaching that just lost their steering. so until they got it under control we got to stop all traffic. >> how it is that traffic was stopped in time, civilian traffic across the bridge? >> that is heroic work of some of our state law enforcement officers. they undoubtedly saved lives with their actions. >> authorities say the ship had lost power and propulsion. you can see the lights go off and on multiple times before it hit the bridge. shipping company synergy marine group says the crew did not suffer injuries, and it's cooperating with the investigation. president biden vowing the bridge will be rebuilt. >> it's my intention that the federal government will pay for the entire cost of reconstructing that bridge. >> while the governor telling me he's met with the families of the missing. >> it was heartbreaking. when you're working on a bridge, you don't think that's a dangerous place to work. >> i heard you stress over and over again this is still a search and rescue operation. what gives you hope that we may still find people alive? >> the thing that continues to give me hope is a commitment that we made, that we are a place where we say we leave no one behind. and we made that commitment to the families, and we're going to continue searching. >> and as crews press on with their urgent search, we're getting a look at the scale of the disaster from the air. tom llamas joins me. you spent time over this today. it's a really huge area. >> good evening. it is. we flew right over the disaster zone there. is a massive circular perimeter filled with all kinds of ships. but what you sense and what you see immediately when you fly over this disaster is that the port of baltimore is not opening up any time soon. tonight the view from the air over this disaster devastating. chunks of bridge and strips of steel sandwiched across the front of the "dali" cargo ship. crushed containers marking the point where the structure buckled. the rest of the francis scott key bridge under water. late this afternoon, we took off over the crash site. as we fly over this disaster, you can actually see how the bridge collapsed. the cargo vessel crashing in to those concrete pilings, and they essentially cracked, sending the bridge, all that steel into the cargo vessel and then into the river. the search-and-rescue operation ongoing, but experts say the chances of survival are dwindling. the water is 47 degrees, and the bridge was 185 feet, nearly 20 stories above the river. the tides, currents and wreckage could be unstable, yet another challenge for rescue workers. from up here you also get a sense of how big this ship is. it's about 950 feet long. to put that in to perspective, it's about the size of the empire state building. when you look at the deck, nearly every inch of it is covered by containers stacked ten high. >> when i got the phone call, i thought it was fake. >> reporter: just hours before the collapse, longshoreman shawn jackson was loading cargo on to the ship. did you notice anything with the ship or crew when you were loading it? >> no, i did not. just a regular day. i would never thought in a million years that would happen. >> reporter: how dark is it out here at 1:30 in the morning? >> it's dark. even in daytime, you really can't see through the water because it's murky, you know. so at nighttime, it's even worse. >> reporter: tonight we're learning more about that missing construction crew that was on the bridge. contractor jesus campos worked with the missing men. he says they're from mexico, guatemala, el salvador, and honduras. they came to baltimore for a better life and have families waiting at home. he says they were good people, people who came here to work. tonight he is praying for a miracle. tom llamas, nbc news, baltimore. we turn now to the investigation, which will be led by the ntsb. the agency will be looking at why the ship apparently lost power as we're already seeing major impacts on shipping. here is tom costello. >> reporter: it was pitch-black as the "dali" left port headed out to sea, traveling at 8 knots, just over 9 miles per hour, it took just four minutes from the first signs of trouble to the moment the ship crashed into the bridge. at 1:24 a.m., the lights suddenly went out on the ship's deck. they came back on a minute later as dark smoke started billowing from the stack. at 1:26 a.m., the "dali" appeared to turn, but at the same moment, the lights went out again. two minutes later, the at 1:28 a.m., the ship collided with the bridge. the super structure quickly crumbling into the river below. >> we searched the best we could this sunken vessel. >> reporter: among the questions for investigators, did the bridge have sufficient barriers to support its support structures? >> once the bridge is impacted directly in one of its piers, key bridge or another bridge, that's going to be the end. >> reporter: under u.s. law, ships entering and leaving u.s. ports use a local pilot to help navigate the waterways. >> they have all the knowledge of the waterways. they memorize the charts. they can literally draw the chart from scratch on a piece of paper. >> reporter: early this morning, a local pilot was on the ship. >> there is nothing worse on the bridge of a ship when everything goes quiet. >> reporter: already tonight, ships that can't get in are backed up outside baltimore harbor. now 24 ntsb investigators are on the scene. they will recover the ship's data recorders, examine the ship's safety and maintenance records. >> any sort of maintenance that was done to a vessel. >> reporter: an online database shows the ship has had 27 inspections since 2015, with two deficiencies found. last year a problem with propulsion, and 2016 the ship hit the port in antwerp, damaging its hull. because the ship is flagged to singapore, a team from that country is also responding. built in 1977, the francis scott key bridge was constructed to handle heavy traffic. experts say removing the wreckage from the water, then rebuilding the bridge could take years. and tom, we understand the fbi is also involved in the investigation? >> the fbi says there is no indication of terrorism. the fire department says no indication of pollution in the water at this point, but we're going see a major impact on the supply chain. cars and products from europe and abroad not able to get in, and carnival cruise lines just announced they will move their operations for now out of baltimore down to norfolk for the foreseeable future. lester? >> all right. tom costello, thanks. meanwhile, in washington, arguments at the supreme court today on the issue of abortion and the effort to limit access to abortion pills, the most common method of abortions in this country. here is laura jarrett. >> reporter: hundreds rallied outside the supreme court today as inside the justices threw cold water on an effort to roll back access to the most commonly used abortion pill in the country, mifepristone. on the market for more than two decades, the pill now increasingly used. but a group of doctors and advocates against abortion rights successfully sued last year to make the pill harder to obtain, the first time a court ever invalidated an fda-approved drug. >> the fda violated several law in its duty to keep women safe. women are now left to receive these drugs in the mail or in their dorm room without ever having been checked by a doctor for life-threatening conditions. that's reckless. >> reporter: today the justices appeared highly dubious. doctors who never prescribed mifepristone and can't be forced to under federal law have the legal standing to sue. >> i don't think you have it for either one of those doctors. >> reporter: the legal fight over mifepristone now focused on the ways the fda made the drug more widely available, including allowing pills to ship by mail, women to use it later into their pregnancy, and other health care providers to prescribe it, changes that if not upheld would limit access to the pill, particularly in red states where in-person abortion procedures are now largely cut off. the biden administration and drug manufacturer urging the justices that secondguessing the fda here could jeopardize approval of any drug on the market. >> we won't go back! >> reporter: back outside -- >> i came out here today because i want to see the abortion industrial complex be dismantled. >> reporter: melanie salazar came from san francisco. >> i have hope that one day we can live in a united states that is abortion-free in all 50 states. >> reporter: others, like alyssa greenwood, a mom of two who came to court the day roe was overturned, back today with her new now 2-year-old. >> i want her to look back as an adult and say we stood up on the right side of this. for all i know, i get pregnant and i don't want to be, or i get pregnant and i can't carry it to term and it's a danger, and i have to be alive for my kids who are here. >> reporter: the court is expected to issue its decision by june. lester? >> all right, laura jarrett, thank you. president biden and vice president harris making a rare joint appearance in the campaign trail today in battleground north carolina. their message highlighting a debate over whether states should expand access to medicaid. our gabe gutierrez is there. >> reporter: darcy will was recovering from a car accident. she says the $700 a month for health insurance was unsustainable. how terrifying is it to not have insurance? >> i -- didn't know what i was going to do. >> reporter: but in december, she was among the 600,000 people in north carolina newly eligible for medicaid after the state expanded the program as part of obamacare. now adults ages 19 through 64 who earn a little more than the federal poverty line are also covered. >> there are no words to describe the relief, because i was -- i have multiple sclerosis. >> reporter: in a rare joint appearance on the campaign trail, today president biden and vice president harris visited this critical swing state, making a push for rural voters over health care. >> that's why the affordable care act is so important. >> reporter: democrats have argued by not expanding medicaid, the state was leaving more than half a billion federal dollars on the table each month. >> access to health care in rural communities is going to be more stable. it also means we're going to have a healthier workforce. >> reporter: but ten other states are still holding out, among them florida. >> there is a significant cost. >> reporter: republicans in florida argue expanding medicaid is fiscally irresponsible and takes resources away from more vulnerable populations. >> we don't want a group of able-bodied working aged adults coming in and impacting health care for those kids and also people with disabilities. >> reporter: but as the 2024 campaign ramps up, democrats see health care as a winning issue. also on the trail today, independent presidential candidate robert f. kennedy jr. announced his running mate, silicon valley attorney nicole shanahan. lester? >> gabe gutierrez, thanks. in 60 seconds, the bombshell raids on sean "diddy" combs' properties. we'll have new details of what was found inside, plus how his attorneys are firing back tonight. before my doctor and i chose breztri for my copd, i had bad days. 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>> yeah. >> reporter: his parents say he made friends everywhere, which helped him as a journalist. >> he was mostly interested in people and telling people's story. >> reporter: when evan decided to move to russia in 2017, they were excited for him, visiting him six years ago. >> we saw russia through his eyes. we were with such a great guide to new russia that we didn't experience before. >> reporter: everything changed when vladimir putin invaded ukraine. evan relocated to london, still often reporting in russia. but last march, his mother got an unsettling call. it was evan reporting in a remote russian city. >> he said that he needs to finish this story. and he'll go back next week. >> reporter: two days later, he was arrested, accused of espionage. >> it was -- it's hard to feel anything, hard to think about anything. >> reporter: the white house calls the charges ridiculous. his parents are grateful for the administration's support, but say that's not enough. >> evan is not here. it's been a year. >> it's been all four seasons, there it's he spent his birthday and all the holidays. >> reporter: in a courtroom visit, they spoke to him through a glass cage in russian, with guards monitoring every word. but still, his family remains hopeful. >> we are keeping ourselves optimistic. that's the best way we can cope with it. no pessimism. pessimism will kill all the open. >> reporter: if you could talk to vladimir putin, what would you say? 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