He bailed out seconds later. Then a street vendor — wearing an “I love New York T-shirt” — waved down a mounted officer, who saw the white smoke collecting inside the still idling vehicle and made a call that got the bomb squad there by about 7 p.m.

It took the bomb squad, according to court papers, eight hours of work simply to render the S.U.V. safe enough to approach. Once the authorities did, they found keys hanging from the ignition. Hours later, after they towed the car to a Queens forensic garage, they found an even more important clue when a police Auto Crime Unit detective crawled underneath the vehicle.

“The break in this case took place when a New York City detective was able to go under the vehicle and get the hidden VIN number,” Mr. Kelly said at a news conference in Washington on Tuesday. “This identified the owner of record, who in turn, as we know, sold it to the suspect.”

It had been something of a feat to get the city’s most senior officials to the scene of the attempted bombing.

Mr. Kelly had been in Washington, for the annual White House Correspondents Dinner, when his cellphone rang. At 8 p.m., he walked over to where his boss, Mayor Michael R. Bloomberg, was sitting and spread the news. At 10:55 p.m. the two men left, taking the mayor’s private jet and touching down at 12:20 a.m. at La Guardia Airport.

Fifteen minutes later, the two men, still in fancy suits, were inside a drab storage area of a building on West 44th Street, pulling up folding chairs with police and F.B.I. investigators around a Formica table and reviewing X-ray photos of the Pathfinder’s contents.

Image The Shelton, Conn., home where Mr. Shahzad once lived. Credit... Christopher Capozziello for The New York Times

And soon, investigators fanned out to find the driver.

All Sunday afternoon, the agents and police searched for the Pathfinder’s owner of record — a man they knew had bought it used from a lot in Connecticut. By 6 p.m., they found the man, in Bridgeport. He said it was his daughter they needed.