We know it is impossible to predict what you would do of -- -- snatched your car -- still in it. But you're about to find out the man whose life changed in an instant when he says those Boston bombers... See More
We know it is impossible to predict what you would do of -- -- snatched your car -- still in it. But you're about to find out the man whose life changed in an instant when he says those Boston bombers took him hostage. As the two Brothers reportedly talked to each other but everything from -- to music. To what they were planning next would that -- little bombs the carjacking victim was quietly trying to figure out how to save his own life. Perhaps hundreds more here's Dan Harris tonight. With each passing day after that Boston marathons not that there is one event that further emerges as a truly pivotal moment. It happened here -- and otherwise and remarkable gas station one young man. Bringing desperate act and he beat them -- instinct when the tide of terror. Started to -- if this guy hadn't escaped and called cops. These two young -- suspects could still be they're hurting innocent -- it's very true. We put his life on the line and who worked out for him and didn't -- got -- some. Real good information. Thursday night a week ago hours after their photos are released authorities say -- too young bombing suspects -- and MIT police officer and then move on to their next victim. A young man known as Danny. He pulled over to send text message -- to a reporter Eric -- it's interviewed Danny. It just. You know these two new Mercedes -- apartment with friends is working on a -- in Kendall Square which is kind of like Boston Silicon Valley. We walk through the events of that fateful night with former FBI profiler Brad Garrett will does -- someone walking up to his passenger -- Not that we'll look at. It would -- -- biggest mistake -- life the young man who rolls down the wind down. His first series isn't side opens the door it's steps -- and. Danny is now in the hands of the alleged terrorist -- on -- -- -- -- -- lies intersecting both men are 26. Both immigrants. But within hours one of them will be again -- -- about killing at MIT officer and then makes it even more chilling -- He -- then the following that happened at the marathon. And the guy said of course yes he said I did -- he didn't takes his semi automatic weapon -- the magazine. Game shows and I don't think he's got -- sky and saying I'm -- Danny is forced to drag -- the dark streets in Greater Boston yeah he's told to stop and pick up another passenger. Media is they younger star and I -- brother Jeff harder Danny now carpooling with the two most wanted -- on the planet. They loading his Mercedes with -- explosives including another one of those pressure cooker bonds -- Not until -- the younger brother. He's oh my god. This is the guy this is -- skinny guy with the hair -- mean the one we've -- you've got a stranger with a gun in your car police just told you he committed. A horrible act of terrorism. And and you have no idea what's gonna happen at exactly other then you probably think you're going to -- The -- says the Brothers rob him but he's only at 45 dollars on him which is not enough. This security camera catches your car and an ATM using the victim's bank -- Danny tells the Boston Globe that during his ride with the Brothers did talk alternates between mundane guys does he -- -- not use the radio and. -- -- -- -- -- -- That the older brother was growth and was once -- more -- in any younger brother he described his. More like a student and a little bit sort of -- fear and more marveling at like buy these -- really cool well what you -- what -- your phone do that kind of staff. At one point during the induction Danny gets a call from a friend. Danny answered the call and they say if you say we're in Chinese will kill you because they know that he speaking Chinese -- can understand it he could be saying you know I'm in a Mercedes. I'm in my car and with the Brothers from the -- call the police so he says in English speaking to his friends speak Mandarin and which would never do otherwise thing I've got to go and six everything. He hangs out contaminants is good boy could check up. Get a sense of what the brothers' plan was at this point. No and I think the problems in is they never had a plan this is where police say their raising carjacking starts to go back. Getaway car he's out of yes they stop at this shell -- in Cambridge -- risky move -- -- this is a neighborhood where they're -- It turns out to -- a decisive moment. So at this moment sitting here and is gas station. The carjack victim makes what may be the most consequential decision of his life absolutely younger brother Jeff -- goes into pay for gas. Now it's just getting older brother in the front -- And in that moment -- realizes that Cameron. Let's put the gun inside pocket of the Mercedes driver -- -- now holding anymore he's playing with the GPS with both hands and Danny realizes. Nationally chance just one brother no guns out of me to bring forward he rehearses in his head to see how -- -- -- -- and slamming. And finally he goes he does it. Chamberlain grabs for Danny but mrs. with the killer right behind and Danny makes himself a moving target and he's gonna get any shot off he's got to be. Over the -- over the backseat through the back window and -- running along the car. Between the gas company car crosses the street to second guess -- Friend just praying at the torture and it's -- lights. George -- gets inside. At a breakfast here -- -- -- one and runs into storm PC and that these -- -- -- -- And again day ahead bay won't they -- -- -- -- -- chart for -- is behind the counter when Danny arrives with his breathless story of being carjacked. By terrorists. Sargent Danny is desperately looking for high so its brands into the storage area in the back. -- realizes if a bomb goes off series could ignite the gas station and -- -- entire neighborhoods. I still -- -- decision. -- -- -- -- Benedict quoted the -- big bone meal -- illicit -- within bullies don't target with a carjacking victim on the phone and almost as soon as he hangs up. Army that I was five minutes everybody seen this yet -- -- -- The break the law enforcement and waiting to. Danny has left his cell phone in the car and everything. -- it -- and the police now have not one but two possible ways to -- his brother and on alert by charging Fannie and start doing just that. It -- -- this signal the Mercedes in the nearby several of water and that is where you can't really killed in the shoot out. Your heart wounded and later captured. Danny's hair raising escape raises -- real question now what should you do in this situation. What's your advice ambulance here in a moment like this and you've got some an armed person in your car what is the right call you sort of have to -- -- Your personality and abilities with the situation. Victims in other carjackings have taken matters into their own hands when -- -- very proud of look at this surveillance tape of a carjacking at a gas station in 2010. There's a baby in the back -- -- the parents -- and that's -- -- And mother Melanie -- -- on the side of the -- everything John Stevens signs. We've just sitting upside down on the passenger seat kicking him in town and that my babies in the high. Feeling. My car carjacker runs off. -- and parents are fine. And check out this incredible video from Tampa Florida -- and the passengers he's not this -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- you have to be reasonable doubt that because you could basically get yourself killed by trying something unlike. Most carjacking victims Danny the young man and -- Mercedes SUV is not just saving himself or his loved ones his actions had much wider consequences. Police now say they believe the Brothers were planning to head to New York City to set off more bombs in Times Square. This -- kind of a bit of an unsung heroes at this point. Yes I think he hasn't really come forward so -- hasn't got the recognition that some other people but -- --
This transcript has been automatically generated and may not be 100% accurate.