"He fell down, screaming, 'Please, please call ... the police. They want to kill me. They have a gun, they have a bomb,''" Tarek Ahmed, the clerk working in the gas station at the time, told CNN's Piers Morgan.
Danny first hid at the front counter, then went to a storage room. Ahmed, after first making sure this man wasn't one of the bombing suspects and separately thinking he might be drunk, quickly picked up a phone and called 911.
"I was waiting (for) someone to shoot me at this moment," Ahmed said, adding he couldn't see outside from where he called. "I was waiting to die ... I wanted to finish my call very fast with the police."
Within five minutes, the gas station was teeming with police. And a short time later, after a chase in which the suspects allegedly shot at police and threw bombs out their windows, Tamerlan Tsarnaev was dead. His brother was captured about 20 hours later.
James Alan Fox -- a criminology professor at Northeastern University, where Danny had been a student, and who has spent considerable time with him over recent days -- told CNN that the carjacking victim "doesn't like to see himself as a hero."
"After all, he says, 'I was only trying to save myself,'" Fox said. "But ... his actions, his composure, his smarts were what led this case to a close and may have indeed saved thousands of Americans if we believe, in fact, that (the Boston suspects) had plans to do more bombings in New York City."