"I can't give you the specifics, I can't tell you why they lost surveillance on him," said New York City Police Commissioner Ray Kelly. "It happens, we prefer it doesn't happen."
For at least 90 mintues, surveillance teams lost contact with a man accused of trying to set off a car bomb in Times Square.
"My understanding was that he was lost for several hours and obviously he came very close to getting out of the country," said Rep. Peter King of New York.
Special Section: Terrorism in the U.S.
CBS News has learned that by Sunday night, the FBI had not only identified Shahzad as a likely suspect, but knew of his whereabouts. By 12:30 Monday afternoon, Shahzad was placed on a no-fly list.
Also on Monday, a surveillance team was watching his apartment and monitoring his emails and phone calls. They could have arrested him, but sources tell CBS News they held back - hoping to uncover leads to other possible associates and plots.
By late Monday afternoon, he drove away from his Bridgeport, Connecticut apartment in his white Isuzu Trooper. Sources tell CBS News the surveillance team lost him in traffic as he drove south toward New York's Kennedy airport.
"It's only in TV and the movies where nothing goes wrong," said former NYPD Officer Eugene O'Donnell, now a professor of police science.
Not only had Faisal Shahzad eluded a surveillance team, he was carrying a 9 millimeter hand gun with extra ammunition.
"If they had apprehended him at the airport and he pulled a gun in the parking lot - we could have had FBI agents losing their lives," Rep. King said.
Or, perhaps he could have gone into the terminal shooting. Attorney General Eric Holder was confident the arrest would be made.
"I was never in any fear that we were in danger of losing him," Holder said.
But there are fears this story with a successful conclusion could have had a much different ending.
Video: Shahzad in Times Square