tonight -- >> something exploded or something. there's blood everywhere. we need an ambulance immediately. >> a serial bomber on the loose. >> how many more bombs are sitting on somebody's front step right now? >> inside the hunt for the austin bomber. unprecedented access to body cam footage. >> it's a trip wire. >> what law enforcement found at this home depot to track down the suspect. >> i got goosebumps. i knew. i knew this is something good. >> and the heart-stopping final moments. >> we had to stop him that night. >> got an explosion. got an explosion inside the vehicle. >> six bombs. two dead. 19 days of terror. "nightline" will be right back.

this special edition of "nightline," "19 days of terror," continues. here now, matt gutman. >> my neighbor, something exploded. blood everywhere. bomber held the city of austin . hostage, lock its residents in a state of terror. >> how many more bombs are sitting on somebody's front step right now? >> reporter: six bombs killing two and wounding five others. tonight we take you inside the hunt for one of the most

prolific bombers in american history. >> in the history of this country we haven't had a serial bomber that planted this many devices in a 19-day period. >> every day means he's still out there. >> you are racing the clock and trying to make the madness stop. >> reporter: on the ground and at the scenes with the austin police. >> it's a tripwire. >> reporter: the bomb squad. >> fire in the hole! >> reporter: and with unprecedented access to the government's top law enforcement agencies. >> looked at the chief and said we obviously have a serial bomber, we need to set up a national command post here. >> reporter: but the atf agents and the fbi -- >> the bomber's car was directly over this hedge row in this corner. >> reporter: revealing new and never-before-seen details on how they pieced together the puzzle and how it all came down to this home depot surveillance footage leading them to those gloves that brought them to that truck. and the one specialist who identified the man who eluded them for over two weeks. >> i got to about the seventh name and it was the bomber's

name. >> we've got him. >> reporter: and we're inside the final moments. one final chase. >> i told them, whatever you do, you've got to stop him before he gets on the interstate. >> reporter: austin, texas. a colorful capital city known for live music and barbecue. >> there's a lot of good things going for austin. we bill ourselves as the live music capital of the world. we've got a very vibrant nightlife. most people in austin feel safe about the city. >> reporter: but that sense of security would be shattered on the morning of march 2nd, 2018. >> breaking news in northeast austin. one person is in the hospital after an explosion at a home. >> 911. do you need -- >> hey, i don't know what's going on. my neighbor, something exploded or something. he's -- there's blood everywhere. we need an ambulance immediately. >> 39-year-old anthony stephan house opened a package left outside his door, unknowingly detonating a bomb. >> stephan.

stephan. >> is he breathing? >> reporter: police racing to the scene. and for the bomb squad this would be the first time they had dealt with a real bomb. >> after we were tla few minutes we realized we had a victim and the type of injuries the victim had sustained i think at that point we realized we had some sort of bombing. >> there is no information that we have right now to believe this is anything other than an isolated incident. >> reporter: a most unusual method of murder, one that brought in teams from the fbi and atf to analyze the scene. but all seem to agree that this was a one-off. >> everyone thought that this was one fatal bombing. >> reporter: for the austin police and bomb squad in particular it was already a busy time of year. in a week the south by southwest festival would begin. as seen in these promotional videos, over largest city. then on march 12th -- >> my grandson is hurt. my daughter is hurt.

please hurry. >> they're on their way. >> they opened a package from outside and it exploded in the house. >> reporter: another package bomb had exploded killing 17-year-old draylen mason and injuring his mom. >> as we're getting ready to go in and start processing this scene, that's when the third device functioned. >> reporter: five hours later another explosion would send bomb technicians scrambling. >> when i heard the bomb squad commander say we have another device, i thought in the united states? this normally is what we see happening overseas. >> you guys must have been thinking are we under attack? >> you think -- >> what is happening here? >> yeah. >> hey, guys, back away. back away. >> hey, guys, it might be a bomb. back off a little bit, okay? >> reporter: that third bombing severely wounding 75-year-old esperanza herrera. >> at the third scene is when i looked at the xheef and said chief, we obviously hav a natio command post here. >> all right. serve ready?

it is important that people be vigilant and be aware for things that look suspicious. if you have had a package show up at your home and you were not expecting a delivery, if the package that is delivered to your doorstep looks suspicious in any way, call 911. report it. >> reporter: six days later no suspects would be named as the city remained on edge. chief manley giving another presser, this time speaking directly to the bomber. >> we hope this person or persons is watching and will reach out to us before anyone else is injured or anyone else is killed out of this event. be the real estate sign. >> reporter: an explosion triggered by a tripwire, and when detonated it injured two men. the device concealed by a red sign. >> i walked over kind of towards this area. i don't remember exactly. but i know it was pretty close to here. and there was a bicycle in the

middle of the street, and these two young men were right here on the sidewalk. >> reporter: officer seth modell was among the first on the scene. >> look at them, look at the fence, and realize that i was looking at shrapnel. >> we have confirmed shrapnel. >> i had to start thinking like i was a soldier again in iraq, and i realized that this is a bomb. and i just started walking slow ly. i shined my flashlight just looking, and i just started doing what a soldier would do. and i was like, there's got to being? here. >> it's a tripwire. >> the device was placed on the ground, and he covered it, the device with the sign to conceal it somewhat. the tripwire ran across the sidewalk here and was probably only about three inches off the ground, and it was anchored to a metal stake somewhere around this location.

>> this entire wall was just covered with pock marks from the shrapnel that was propelled from the device. >> it's a tough message to deliver to a community. you're telling them be concerned about anything, i can't give you a description of what that is but if you see anything that looks out of place you need to call us. >> we want everyone within a half mile radius of this intersection of dawn song drive and republic of texas back here in travis country to stay inside your homes until we have had a chance to deem this neighborhood safe. >> reporter: a tripwire, a technique typically used in war zones, it told him that the bomber was growing in cunning and confidence. are you thinking to some degree this is a signal to you that he's toying with you? >> i think it was a signal. we also were very concerned because of the change in the bomb, the sophistication of the bomb, which now led us back to thinking could this be a

terrorist? >> we had people of interest throughout this investigation. and the night of the tripwire device we knew where those people were. and they were nowhere near that. so unfortunately the morning we start processing that scene we were at square one. >> breaking news. a package exploding at a fedex facility. >> reporter: then on the night of march 19th a fifth explosion. this time a package awaiting shipment inside a fedex sorting facility just outside of san antonio. that bomb injuring one employee. >> there were nails and metals in the bomb. package was going to austin. >> reporter: that elevated our concerns tremendously. because now you're shipping something. and before we knew they were placed. >> meaning it could be anywhere in the country. >> and we didn't know how many. >> reporter: it was the bomber's third method of delivery. police had just received their first big break. >> we found out the subject mailed two packages, one of which was now in austin. i called the fedex facility in austin, described the package to the manager, and he said yes, we have that particular box, and he

said it's on the dock for outbound delivery. so at that point i told the manager that is a live improvised explosive device, evacuated building, and then called the bomb squad. >> reporter: by dawn the apd bomb squad had arrived on the scene. >> we immediately sent one of our robots inside and looked at the package, get the tracking numbers off of it, and see that yes, this was it. >> reporter: the package that the bomb squad safely intercepted had been marked for delivery that same day. the tracking number leading the authorities to this fedex store. >> he was wearing a disguise when he walked into the fedex and he was wearing gloves. fedex employee said he went and got into a red ford ranger. >> the fact that he walked in brazenly, that was his biggest mistake. >> reporter: authorities reached out to home depot, where they believed the bomber may have purchased supplies. the home depot organized retail crime division works in tandem with law enforcement for these kinds of situations. >> we are then able to identify those gloves, come up with a

product identification number, and combined with that and the sign is where we were able to generate the one receipt purchased here on round rock. >> reporter: after scouring hours of surveillance footage they found him. >> when he walked into the building he asked the door greeter some questions, kind of asking where certain items were. >> reporter: he purchased a red sign like this reading "drive like your kids live here" used in the tripwire explosion and gloves he would wear to drop off those packages at fedex. he can be seen exiting the home depot and getting into his vehicle. as that information was being called into the command center, a team of fbi analysts immediately started searching for the person who had purchased those supplies and owned that red truck. >> i was systematically going through each name and just looking at what kind of vehicle would this person have. and i got to about the seventh name. it was the bomber's name. and i conducted a search to find out what kind of vehicle he had. it was exactly the vehicle we were looking for. >> reporter: you were taking the

information in real time and actually basically finding the suspect. >> yes. which is why it was a heart-stopping moment. and i got goose bumps. i knew this is something good. >> reporter: finally, what eluded them for 18 days, they had the identity of the bomber. they began the process of preparing search warrants. but it was already late. >> so we decided that we were going to hold and execute that warrant at sunup without making any further notice. >> you never did get to sunup, did you? >> we didn't. >> he's on the move. >> reporter: next, the hunt for the bomber intensifies. >> i told them whatever you do you've got to stop him before he gets on the interstate. >> got an explosion. got an explosion. >> reporter: stay with us. people with type 2 diabetes (anno) are excited about the potential of once-weekly ozempic®. in a study with ozempic®, a majority of adults lowered their blood sugar and reached an a1c of less than seven and maintained it. oh! under seven? and you may lose weight. in the same one-year study, adults lost on average up to 12 pounds.

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this special edition of "nightline," "19 days of terror," continues. here again, matt gutman. a year ago austin was a city on edge. >> the hunt for a suspected serial bomber tonight striking fear yet again in austin. >> reporter: over the course of 19 days an elusive bomber dangled the state capitol on a string. >> we are clearly dealing with what we expect to be a serial bomber at this point. >> reporter: but through painstaking work authorities had identified a suspect, 23-year-old mark conditt. >> it was 1:00 in the morning. i was in the command post. the surveillance team reported we've got them. >> reporter: the bomber had gone dark, but after briefly turning on his cell phone they were able to ping his location, tracking him to this hotel parking lot in a suburb north of austin. >> the bomber's car was directly over this hedgerow in this corner parking spot. i was in that space that's

facing south. i had darked up my lights. i could see the bomber's vehicle from an oblique angle. and i'm going through in my head, how's this going to play out. >> reporter: just down the road members of the city's s.w.a.t. team were staged in another nearby parking lot. >> we had information he was inside the vehicle that was parked. he didn't care who he hurt or killed at this point. we had to stop him that night. >> do you all know if fbi's working this area too at the same time? we can't spook him. >> i had an eerie feeling it wasn't going to end well. >> he's on the move, backing out now. >> i backed out and proceeded behind him as well. apd s.w.a.t. had the two vehicles that were directly behind him, followed him out. >> coming up to 35 ound. he proceeded south on the service road, turned out to go to the frontage road of i-35. >> 35 frontage and old settlers. and he's stopped right now. >> we had quite a few people

pull up behind him. and if you look at the videotape you see a pretty long train. at that point the guy knew. >> reporter: the s.w.a.t. team had one shot, one final chase. >> the idea was that we needed to hit his van hard enough to try to disable his vehicle. >> one of our biggest fears is on impact it was going to explode. so i told them, whatever you do, you've got to stop him before he gets on the interstate. >> all right. the van's made contact with him. >> we exit our van and move up to the vehicle and he detonates an explosive device inside his vehicle. >> got an explosion. got an explosion inside the vehicle. >> initially, i saw the flash and i felt shrapnel or debris or whatever hit my face, and i stepped back. >> i was one of the first up to the windshield area and could see inside. i quickly recognized that our suspect was no longer a threat at that point. >> i can't even describe to you

how bad it felt listening to the radio traffic. i remember distinctly going to a different radio channel to advise dispatch. >> shot taken. suspect's down. >> i'm really lucky that i didn't lose anybody. >> reporter: after 19 days the bomber's grip on the city of austin was over. >> the suspect is deceased. >> but no high fives yet, right? >> no. we knew that we had to hit that house the next morning. >> reporter: it's on this quiet cul-de-sac that mark conditt lived. he and his father purchased this house. they fixed it up and rented it out. but it was in a room in the back that conditt lived and had stockpiled enough weapons materials to blow up the entire block. and it was there that he masterminded that bombing spree. >> he had the capability to build much bigger devices. >> any idea what triggered him? >> that's what everybody wants to know. right? they want to know why. i'd love to know why. the reality is there's no answer and there's no reason that could ever make any of this okay. >> we have nothing to gives us

an indication he intentionally targeted these individuals. >> reporter: according ought u.s. attorney's office, nothing specific seemed to influence the man's decision to kill. >> our law enforcement partners have reviewed all of the evidence and they have found no evidence of links to a hate group or a terrorist group, no evidence of being influenced by any recognized ideology. it may be a mystery what was internally motivating him. >> reporter: authorities say they still have no motive. but the bomber did leave behind a 25-minute manifesto he recorded on his phone. >> he talked about if i think they really know who i am, i walk into a crowd at mcdonald's and blow up everyone that's in there with this last bomb that's in my pocket. >> reporter: did he ever express remorse? did he ever say i'm sorry? >> in fact, he purposely said he has no remorse. on that tape there is no mention of terrorism, hate crime. he says he's a psychopath and he likes killing people. >> reporter: although excerpts

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♪ the city of austin is still healing. victims' families still left with the shockwaves of pain. >> i miss him so much. >> reporter: as loved ones continue to mourn the lives lost, austin is still pondering the demented actions of one man as they return to breathing again. >> we move up to the vehicle. he detonates a bomb. >> the heroes who stopped the killer who held the city of austin hostage for 19 days. >> it's a tripwire. >> all hands on deck. >> the clues. the home depot video. that truck. and the agent who connected the dots. >> it was exactly the vehicle that we were looking for. >> inside the investigation.

the takedown of the bomber. now streaming on hulu.

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