[ cheers and applause ] and applause ] tonight on "nightline," inside the las vegas massacre. >> make your way up. armed units only. >> the chilling moments you've never seen. >> breach, breach, breach. >> clear. >> the stories you haven't heard. the "nightline" documentary more than a year in the making. exclusive access, shrapnel and bullets were flying down this hallway. and heart-pounding body cam videos. heroes of that night speaking for the first time. >> almost there, man. hang on. >> he said, what are we doing? i said, let's go. we got to go back. >> and incredible stories of survival. >> i could hear the gunfire.

i could see everybody. >> the special edition of "nightline," "a killer on floor 32" will be right back. be right back.

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one of uncommon heroism. and terror from the gilded tower that looms above. >> hundreds of people running everywhere, fear this was just going to be the first part of a multifaceted attack. >> reporter: over the last year, much of that night has remained a mystery. >> we're trying to get more. >> reporter: at first, all we knew was what we saw captured on cell phones. but after a ten-month long investigation by law enforcement, in coordination with mgm, using surveillance cameras, body cameras, and a 3d model, we can now present one of the most comprehensive views of a mass shooting ever. exposing gaps in our system and showing the response, moment by moment.

september 25, 2017, security camera footage captures steven paddock arriving at the mandalay bay resort and casino six days before the attack. he's a high roller, a regular at the hotel. >> he was a very typical guest. he was, in our estimation, the lowest risk type of individual. >> no alarm bells going off. paddock checks into a suite on the 32nd floor and he's given the vip treatment, allowed to bring his luggage up through a service elevator. over the course of his stay, he makes several trips to his house in mesquite, nevada, and brings in case after case after case. 21 suitcases in all. full of guns and ammunition. the investigation shows on october 1st, he orders room service and rigs surveillance cameras. before he brings in a final batch of suitcases and locks himself in his room. that night, at 9:40 p.m., mandalay bay security officer jesus campos is on a routine

security check, assigned to a room alarm on the 32nd floor. >> this was the last call of my night. >> reporter: you were heading home in your head. >> in my head, i was home free after this. >> reporter: he has no idea he's about to become an accidental hero on what would become one of the most horrific nights in american history. as shown in this rendering, once on the 30th floor, he takes the stairs up to the 32nd, but he finds the exit door jammed, so he walks up to the elevator and takes it back down. >> reporter: when did something seem off to you? >> when i noticed the metal l bracket that was secured -- that holds the door secured. >> reporter: that bracket, strategically placed there by a man staying in the suite just a few feet away. >> i didn't know what was going on, just simply because that's not normal. i had to call our security dispatch. i was transferred to engineering dispatch. >> reporter: as he walks back into the hallway to check that room alarm, turns out a nanny a few doors down left their door

ajar. he hears a strange noise coming from the suite. >> i thought it was drill noises. >> reporter: the massacre has just begun. across the street, just moments before, jason aldeen had taken the stage in the final night of the route 91 harvest festival. metes ♪ >> reporter: bullets rained down on the 22,000 concert goers packed into the open air venue. >> that's just a fire cracker. >> why would you do that? >> confusion mixes with panic. >> there's people running everywhere. nobody knows where to go. >> reporter: in under a minute, over 100 rounds are fired into the crowd. concert goers flood 911. >> there's numerous reports coming in. we have 33 calls holding. it's an active shooter. >> it's fireworks. >> reporter: as the shooter launches his attack back on the

32nd floor, campos, who is unarmed, continues walking down this hallway. he passes a room service cart with the surveillance camera. it's either that or the sound of the stairway door that alerts the shooter. he fires through the door. suddenly you're under fire. >> yes. i went to go lift up my pant leg and i saw the blood coming down. >> reporter: campos takes cover in this doorway alcove and radios for help. >> there's shots fired at 32135. >> reporter: the shooter turns back to the concert goers below and fires over 250 more rounds in the next 4 minutes. las vegas metro police officers respond to the scene. >> we have multiple casualties. multiple casualties. >> get behind cover.

>> reporter: but they too come under attack. >> can you see where it's coming from? >> no. >> reporter: pinned down by automatic gunfire. >> i'm down. i'm down. >> reporter: the echo of gunfire through the strip leads to mistaken reports of shooters in multiple hotels. deputy chief andrew walsh responds to the scene. >> what sticks with me is that fear, that pain in my stomach that this was going to just be the first part of a multifaceted attack. >> we're getting reports of shots fired at tropicana. >> reporter: back in the hotel, steven, an engineer, is riding an elevator to the 32nd floor in response to campos' earlier call about that l-bracket. pushing his maintenance card, he walks out of the elevator and straight into danger. >> i noticed him. i said, get cover. it's not safe. at that moment in time, there was more rounds being dispersed. >> reporter: suddenly, schuck

himself is under fire. >> something hit me in the back as i was jumping into cover. >> someone's fired a gun up here. someone's fired a rifle on the 32nd floor down the hallway. >> reporter: the mandalay bay security office hears schuck's alert and hustles toward the elevators. >> i thought if i don't come out of this hallway alive, i wanted to communicate for metro and first responders to get up there because this is where the shooter is. >> reporter: every second that schuck and campos are under fire on the 32nd floor is a chance for the concert goers below to flee. >> we're going to get trampled. >> reporter: for paige, running was an agonizing choice. she and her mother were both shot. >> we rolled her over, and a retired firefighter came over, and he told us that we had to go. he said that if we wanted to live that we needed to go. i looked into his eyes, and he

said, you need to go. >> reporter: paige and her sister fled, leaving their mom behind in the care of a stranger. >> once i was shot, i fell down. stephanie and paige were hanging over me saying, mom, just screaming my name, mom, and next thing i know, my body just floated. floated up. i could hear the gunfire. i could see everybody. i could see my own body laying down there. the next thing i know, i was in heaven, and i saw my dad and my two brothers and my uncle, and it was so beautiful. it was so beautiful. you didn't want to come back. they just told me, it's not your time rose marie. you got to go back. tfs n it's not your time. so next thing, i woke up, i was on a gate that they put me on to drag me to the ambulance.

>> reporter: that retired firefighter kept his word, getting her to safety. >> come on, guys. >> reporter: hundreds flood into the nearby streets. >> is she shot too? >> reporter: they set up makeshift triage wards. >> relax. relax. >> he's not shooting anymore. >> reporter: the situation so dire, police officers step in as paramedics. >> you see officers stopping to render aid. you see officers bleeding from bullet wounds. >> they're all coming right now. >> she got a gunshot to her lungs. >> reporter: in the midst of the chaos, police worked to keep everyone calm. >> hang in there, please. hang in there. you guys are going to be okay. we'll be back. >> reporter: stay with us. stay with us. ♪ cleaning floors with a mop and bucket is a hassle, meaning you probably don't clean as often as you'd like. for a quick and convenient clean, try swiffer wetjet. there's no heavy bucket, or mop to wring out, because the absorb and lock technology traps dirt and liquid inside the pad. it's safe to use on all finished surfaces

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this special edition of "nightline," "a killer on floor 32," continues. >> reporter: october 1, 2017, las vegas metropolitan police are responding to reports of an active shooter at the route 91 harvest festival. rookie brandon and veteran officer cole were just beginning their graveyard shift when the massacre began. >> fully automated fire from a elevated position. take cover. >> while we're driving there, we can hear ery time somebody keys up their microphone on duty, we can hear automatic gunfire. as soon as we show up, it's time to go to work. tried to help anybody we could right off the bat. >> keep going. everybody, keep going.

[ bleep ] >> and then that's when we met frank. he came over to our car and he's carrying his wife, jovana, in his arms, and he said, hadiya pendleton help me, i'm a police officer. >> she appeared lifeless. at that point, we obviously knew this was very critical. >> hold that door. let's go. >> female with a gunshot wound to the head. >> we're almost there, man. hang on. >> hurry up! >> just driving as fast as we can and frank's in the backseat and he's yelling at jovana to hang on. >> one minute, man. one minute. >> keep talking to her. make sure you do chest compressions, man. >> i remember banging on the window and i hear brandon in the front, and he's telling me, keep going chest compressions and

we're almost there. >> at this point, she had blood -- she was bleeding everywhere, like her entire body was covered in blood. and we carried her into the emergency room and i just remember yelling, hey, i have a gunshot wound to the head. where do you want her? >> right here, right here. >> we set her down and that was like the first moment that you had to -- a chance to take a breath and i looked down and i'm covered -- covered in blood. i looked at brandon. he said, what are we doing? i said, let's go. we got to go back. >> shannon, call the police. someone's firing a gun up here. someone's firing a rifle on the 32nd floor down the hallway. >> responding to 32. >> reporter: inside the mandalay bay, steven schuck, the engineer, pinned down on the 32nd floor with security guard jesus campos, have alerted

authorities to the shooter's location. >> we're at the top right now. >> reporter: police spread out, sweeping through the hotel. >> cover your head. >> show me your hands. >> reporter: ten minutes have passed since the first gunshots. by this point, the shooter has gone quiet. on the 32nd floor, schuck and campos escape to safety as police and security work to get the guests out of their rooms. >> metro police, let me see your hands. hands! >> go, go, go. run. >> let's go. >> ready? >> watch for booby traps. nobody comes out of the building. >> you got long? i got shotgun too. >> copy. we should be a floor below you. >> reporter: one floor below, a s.w.a.t. team makes their way to that stairwell. >> shield up, shield up. you guys doing a [ bleep ]

phenomenal job, by the way. beers are on me later. >> reporter: right next to the shooter's room, they game out how to make entry. they force open that bolted door. and rig the door to the suite with an explosive strip. >> stand by for breach. >> reporter: then, a warning. >> breach, breach, breach. >> everyone in the hallway needs to move back. all units move back. >> breach, breach, breach. . >> okay. over on that. in with you. >> clear. >> reporter: they find the shooter dead by a self-inflicted gunshot wound. >> cameras up on the peepholes and all that.

that's what these are. >> reporter: in both rooms, over 1,000 gun shell casings. he still had over 5,000 rounds of live ammunition. for more than a year, this hallway leading up to the shooter's suite has been sealed off from public view until now. >> chunks of wall are missing because it's been taken out as evidence because shrapnel and bullets were flying down this hallway, shot from all the way in the other end. >> reporter: behind this door, investigators found 24 weapons from ar-15s with bump stocks to ar-10s with armor piercing bullets. >> a person can, in our country, can go out and buy that many weapons and not break the law until one of those kills a human being. it's a challenge for law enforcement. >> reporter: and just today, the justice department moved to officially ban bump stocks, but gun rights advocates immediately filed suit to stop the ban. the final toll, staggering. 58 dead.

more than 850 injured. >> it's hard to comprehend what happened, even to this day, after the shooting we went back and then our next job was to clear the concert grounds and look for anybody who was still alive and hiding. then after that was done, our job for the rest of the morning was actually standing over -- standing over some people who were passed away until the coroner could come pick them up until about 8:00 in the morning. >> reporter: later that morning, they head back to the hospital to check on a wounded officer and the young woman they had carried in. >> going to the hospital and learning that she's actually still alive was kind of like sunshine to a dark day.

>> i saw it in their face that they were -- they were hurt by this and they could -- i kept telling them, you know, be proud. you know, you guys got my wife here. >> reporter: for frank and jovana, their swift actions meant the difference between life and death. >> there's nothing but love for those two guys. >> yeah. for sure. i -- i am speechless. i don't know what words to say to them. that i'm grateful. they saved my life. >> reporter: we'll be right back. t back. >> announcer: this special edition of "nightline" is sponsored by mercedes-benz. ercedes-benz. whoa! the mercedes-benz winter event is back, and you won't want to stop for anything else.

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♪ i feel like i got a second chance and 58 people didn't, and i need to live a good life to honor them.

♪ >> reporter: our full length documentary, "a killer on floor 32," has even more stories from that harrowing night and is now streaming on hulu. thanks for watching "nightline." good night, america. ight, america.