MIAMI -- A federal air marshal fatally shot an American Airlines passenger yesterday who allegedly said he had a bomb in his bag at Miami International Airport. It was the first fatal shooting by an undercover agent since the sky marshals' ranks were rapidly expanded after the terrorist attacks of Sept. 11, 2001.
Federal officials said there was no evidence that the passenger, 44-year-old Rigoberto Alpizar, was a suspected terrorist. Department of Homeland Security officials said Alpizar ignored two air marshals' orders to get down on the ground and he appeared to be reaching into his bag when one of the marshals fired.
No one else was reported hurt, but officials ordered all passengers off the plane, removed all of the luggage, and blew up two bags belonging to Alpizar on the tarmac as a precaution.
A Homeland Security spokesman, Russ Knocke, said that the marshals ''took appropriate action" and that the decision to shoot was ''consistent with their training."
The Miami-Dade County Police Department is investigating the shooting, and the FBI said yesterday that it is investigating whether the case was related to a terrorist plot.
''We're looking to see if there's a nexus" that might involve terrorism, said Andy Apollony, an FBI assistant special agent in Miami.
''Right now, we're not seeing it, but we continue to look," Apollony said. ''Anyone who gets on a plane and says they have a bomb, we are going to keep looking at it."
A woman who answered the phone at Alpizar's residence in Maitland, Fla., said she had no comment. Relatives said Alpizar and his wife had been on a working vacation in Peru. A neighbor who said he had been asked to watch the couple's home described the vacation as a missionary trip, the Associated Press reported.
Several supporters of the air marshal program praised the marshals' actions, but the shooting is likely to raise questions about the expanded presence of guns aboard commercial airplanes in recent years, as well as the marshals' training -- in particular, with persons who may be mentally unstable.
Air marshals do train on how to deal with unstable passengers. ''The difficulty of the job is you have a split second to make a decision," said Brian Doyle, a spokesman for Homeland Security.
Much of the air marshals' work remains a mystery because many details about the program, such as where the marshals fly, how many there are and even their names, are considered confidential. The nation had only 33 sky marshals before the Sept. 11, 2001, terrorist attacks and the program was expanded rapidly to several thousand marshals, who fly in teams of two on many flights in and out of Washington and New York airports. Through international agreements with foreign countries, they also fly on a number of international flights.
The drama in Miami unfolded before the flight had begun. All 114 passengers had boarded American Flight 924 scheduled to depart Miami for Orlando yesterday afternoon when Alpizar, a Florida resident traveling with his wife, said he had a bomb in his carry-on bag, officials said.
Alpizar had arrived in Miami from Quito, Ecuador, earlier that day and had stopped in Miami to board the second leg of his trip to Orlando, federal officials said.
Several witnesses said they saw Alpizar run from his seat near the back of the plane toward the cockpit, where air marshals confronted him. A passenger, Mary Gardner, said she saw the man identified as Alpizar run up the aisle, and he appeared to be panicked, she told WTVJ-TV in Miami.
As his ran, his wife screamed ''My husband! My husband!" and said that her husband was bipolar and had not taken medicine, Gardner told the station.
Federal officials said two agents confronted Alpizar in the jetway as he left the plane.
Officials did not disclose how many shots were fired or where Alpizar was hit.
All of the passengers were initially ordered to put their hands on their heads and were led off the plane that way.
They were put on buses and many were questioned. Airline executives said the passengers eventually were allowed to go on other flights to Orlando.
The shooting shut down one terminal for a short time, but never closed the airport. The case also brought heightened security at airports around the country.
At Logan International Airport, officials called in additional State Police troopers -- some conspicuously toting automatic weapons -- to patrol the terminals.
A Massport spokeswoman, Danny Levy, called the beefed-up security a ''prudent" response.
''We have escalated our defense at the airport until we ascertain the facts about what happened in Miami," she said.
Federal and local officials are still determining which agency will the lead the Miami investigation. The FBI takes the lead when investigating crimes aboard aircraft, but federal officials said that Alpizar's body fell onto the Jetway even though air marshals fired their weapons from the plane.
Air marshals are trained to declare themselves only as ''police" when they respond to a security or safety incident aboard an aircraft or in an airport. Several news reports have detailed cases in which air marshals have blown their covers to help police.
Ralph Ranalli of the Globe staff contributed to this report. Material from the Associated Press was also used.