The man, identified as Rigoberto Alpizar, a 44-year-old U.S. citizen, was gunned down on a jetway just before the American Airlines plane was about to leave for Orlando.

The passenger indicated there was a bomb in his bag and was confronted by air marshals but ran off the aircraft, Doyle said. The marshals went after him and ordered him to get down on the ground, but he did not comply and was shot when he apparently reached into the bag, Doyle said.

The plane, Flight 924, had arrived in Miami from Medellin, Colombia, just after noon, and the shooting occurred shortly after 2 p.m. as the plane was about to take off for Orlando with the man and 119 other passengers and crew, American spokesman Tim Wagner said. Alpizar had arrived in Miami earlier in the day from Ecuador, authorities said.

After the shooting, investigators spread passengers' bags on the tarmac and let dogs sniff them for explosives, and bomb squad members blew up at least two bags.

No bomb was found, said James E. Bauer, agent in charge of the Federal Air Marshals field office in Miami. He said there was no reason to believe there was connection to terrorists.

The concourse where the shooting took place was shut down for a half-hour, but the rest of the airport continued operating, officials said.