MIAMI – An agitated passenger who claimed to have a bomb in his backpack was shot and killed by a federal air marshal Wednesday after he bolted frantically from a jetliner that was boarding for takeoff, officials said. No bomb was found.

It was the first time since the Sept. 11 attacks that an air marshal had shot at anyone, Homeland Security Department spokesman Brian Doyle said. Another federal official said there was no apparent link to terrorism.

According to a witness, the passenger ran down the aisle of the Boeing 757, flailing his arms, while his wife tried to explain that he was mentally ill and had not taken his medication.

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

Alpizar, a 44-year-old U.S. citizen, was gunned down on a jetway outside the American Airlines plane, which was parked at a gate at Miami International Airport. Alpizar had arrived earlier in the day from Quito, Ecuador, and Flight 924 was going to Orlando, near his home in Maitland.

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.

“We’re all still in shock. We’re just speechless,” sister-in-law, Kelley Beuchner, said by telephone from her home in Milwaukee.

The shooting occurred shortly after 2 p.m. as Flight 924 was about to take off for Orlando with the man and 119 other passengers and crew, American spokesman Tim Wagner 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 any 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.

Federal officials declined to say how many times Alpizar was shot, or reveal how many air marshals were on the plane.

Mary Gardner, a passenger aboard the Orlando-bound flight, told WTVJ-TV in Miami that the man ran down the aisle from the rear of the plane. “He was frantic, his arms flailing in the air,” she said. She said a woman followed, shouting, “My husband! My husband!”

Gardner said she heard the woman say her husband was bipolar – a mental illness also known as manic-depression – and had not had his medication.

Gardner said four to five shots were fired. She could not see the shooting.

After the shooting, police boarded the plane and told the passengers to put their hands on their heads, Gardner said.

“It was quite scary,” she told the TV station via a cell phone. “They wouldn’t let you move. They wouldn’t let you get anything out of your bag.”

Alpizar’s brother-in-law, Steven Beuchner, said he was a native of Costa Rica, and met Beuchner’s sister, Anne, when she was an exchange student there. Relatives said the couple had been married about two decades.

Neighbors described Alpizar as a pleasant man who worked in the paint department of a home-supply store and spent his spare time tending to the lawn of his ranch-style house. Many found it incomprehensible that he could have made a bomb threat.

“He was a nice guy, always smiling, always talkative,” Louis Gunther said. “Everybody is talking about a guy I know nothing about.”

Alex McLeod, 16, who lives three houses from the Alpizars, said: “This whole neighborhood is shocked. . Totally uncharacteristic of the guy.”