U.S. air marshals on Wednesday shot and killed an American Airlines passenger who claimed to be carrying a bomb in his backpack and ran off a plane at Miami International Airport after being confronted.

Federal officials said the 44-year-old American made threats and indicated he had a bomb in his bag as he was boarding a flight to Orlando in central Florida.

It was the first time an airplane passenger was shot by air marshals since the U.S. marshals program was beefed up after the September 11, 2001, attacks on New York and Washington. Witnesses said the man might have been mentally ill.

The man, who arrived in Miami from Quito, Ecuador, was identified as Florida resident Rigoberto Alpizar.

Authorities said he was challenged by two air marshals on board the Orlando-bound plane, and shot on the passenger gangway after running off the aircraft. He ignored demands to put his bag on the ground and instead reached into it, a Department of Homeland Security spokesman said.

"Shots were fired as the team attempted to subdue the subject," the spokesman said.

The shooting triggered a scramble by air marshals to guard airports across the United States against possible attacks.

But Jim Bauer, special agent in charge of the federal air marshals' Miami office, said investigators found no immediate evidence of a link to terrorism and no sign of a bomb.

A woman who said she was a witness told NBC television's Miami affiliate, WTVJ, that the man's wife had screamed "my husband, my husband," and said he had bipolar disorder and needed medication.

"Her husband ran through the aisle frantically. She ran after him and all of a sudden there were four or five shots," passenger Mary Gardner told the station by telephone.

Federal officials said they could not comment on the allegation that the suspect might have been mentally ill.

PLANE SURROUNDED

A concourse at Miami International Airport was briefly evacuated and closed down while police snipers, dogs and SWAT teams took up positions around American Airlines Flight 924, a Boeing 757, which had arrived from Medellin, Colombia.

The rest of the plane's 113 passengers were ordered off the plane with their hands in the air and sequestered for questioning.

Some passengers told local media they were treated roughly by police.

"They put a gun to the back of my head and said, 'Put your hands on the seat,"' the Miami Herald newspaper quoted John McAlhany as saying in a story posted on its Web site. "That was more scary than anything."

Passengers' luggage was taken off the plane and laid out in lines on the tarmac, where police dogs were led around sniffing for explosives, television images showed. At least one bag was blown up in a controlled explosion.

Security experts said even if it turned out that the man was mentally ill, the air marshals had acted exactly as they have been trained to in the aftermath of September 11, 2001.

"The man was clearly intent on committing 'suicide by cop,"' said Scot Phelps, associate professor of emergency and disaster management at the Metropolitan College of New York.

"That's exactly what you want an air marshal to do, that's what they're trained to do," Phelps said.

The incident fueled a debate about government plans to water down some of the security measures introduced on airplanes after September 11, when hijacked aircraft were flown into the World Trade Center and the Pentagon.

Small scissors and screwdrivers will be allowed back on planes as the security emphasis shifts more to bomb threats, government officials announced last week.

The U.S. air marshals service said it was the first time one of them had actually fired on a passenger since the program was expanded after September 11.

Security experts say air marshals are held to higher standards of handgun accuracy than officers of any other federal law enforcement agency because of the danger that their bullets could hurt innocent passengers, or pierce an aircraft.

"Historically, the air marshals have been known as the best shots," said Joseph Gutheinz, a former military pilot and retired agent in NASA's inspector general office.

PHOTO CAPTION

American Airlines Flight 924, a Boeing 757, pictured in this image taken from video, sits at Gate 42 at Miami International Airport, December 7, 2005. (Reuters)

Source: Reuters