MIAMI -- A passenger who authorities said claimed to have a bomb was shot to death on a jetway leading to an American Airlines plane at Miami International Airport just after 2 p.m. Wednesday.

According to authorities, Rigoberto Alpizar was boarding Flight 924, which had arrived from Colombia and was continuing on to Orlando. He had cleared customs agents when he returned to the plane while passengers were disembarking at gate D-42 and said he had a bomb in his carry-on luggage.

Alpizar was confronted by air marshals but ran off the aircraft, authorities said. Federal air marshals pursued him and ordered him to get on the ground, but authorities said Alpizar did not comply and was shot while apparently reaching into the bag.

There were two air marshals on the flight, according to officials. Both air marshals fired their weapons, but it has not yet been determined if both hit Alpizar.

FBI Special Agent in Charge Jim Bauer said that Alpizar was shot because he was carrying a backpack and made a threat and the air marshals had no other option.

Bauer said that investigators do not believe there was any terrorism connected to the incident.

Department of Homeland Security spokesman Brian Doyle confirmed that Alpizar, 44, was a U.S. citizen.

A witness said that Alpizar frantically ran down the aisle of the Boeing 757 and that a woman with him said he was mentally ill.

After the incident, reporter Jessica Sanchez said that neighbors in Maitland, Fla. told her that Alpizar has been married for 20 years and has lived in Maitland for some time. They also said that he was bipolar and required medication. His mother-in-law also told reporters that Alpizar was bipolar.

Bauer said that Alpizar had flown into Miami from Ecuador Wednesday morning. Bauer said that the woman traveling Alpizar is believed to be his wife.

The incident occurred as the flight was preparing to continue on to Orlando, Fla., after about a two-hour layover in Miami. Estela Morales, a passenger on the flight who was not traveling to Orlando, said the trip from Colombia to Miami was without incident.

The airport was never closed, but Concourse D was shut down for about 30 minutes, said MIA spokesman Marc Henderson. Air traffic continued as usual by midafternoon.

Police spread the passengers' bags on the tarmac and had dogs sniff them for explosives. At least three bags, assumed to belong to Alpizar, were detonated or shot with a water cannon as a precaution. The Miami-Dade Bomb Squad confirmed that there were no explosives in any of the bags, according to Bauer.

Local 10's Gwen Belton said that the passengers of the flight were led out of the plane with their hands in the air. They were detained and questioned by federal authorities.

It was the first time since the Sept. 11 terrorist attacks that an air marshal had shot at a passenger or suspect, Doyle said.

Transportation Security Administration Director Rick Thomas said that the agency does not believe that the incident had any connection to terrorism, but that a joint task force will continue to look into the possibility.

Air marshals and federal authorities are handling the investigation.