SAN FRANCISCO - A “suicidal” mechanic stole an empty passenger plane from the Seattle-Tacoma airport late Friday, took it for a brief flight that included an aerial loop, then crashed it in an incident officials said was unrelated to terrorism.

Two military F-15s were scrambled to chase the stolen plane, but “were not involved in the crash,” local officials said.

Video taken by a bystander showed the passenger airplane making an unlikely upside-down loop, then flying low over Puget Sound before crashing into the sparsely populated Ketron Island in the northwestern US state of Washington.

The crash sparked a fire in the dense forest. Flames lit up the night as they spread from the burning wreckage to nearby trees. Officials said there were no victims on the ground.

The stolen plane was a twin engine turboprop Q400 airplane belonging to its sister carrier Horizon Air, Alaska Airlines said on Twitter. It normally carries 76 passengers.

“This is not a terrorist incident,” Ed Troyer with the Pierce County Sheriff’s office wrote on Twitter. The plane thief “is confirmed a suicidal male,” Troyer wrote. “We know who he is.”

The suspect was identified as a 29-year-old airline mechanic and local resident who “acted alone,” Troyer added, confirming that there were “no passengers on the plane” when it crashed.

The sheriff’s office also said that the F-15s arrived minutes after the plane was stolen and kept the aircraft “out of harm’s way and people on ground safe.”

Horizon Air chief operating officer Constance von Muehlen issued a video statement describing the incident.

“We believe it (the plane) was taken by a single Horizon Air employee and no other passengers or crew were on board,” she said. “Our hearts are with the family of the individual aboard as well as all of our Alaska Air and Horizon Air employees.”

The plane was stolen at around 8 pm (0300 GMT Saturday) and crashed 90 minutes later, officials said.

John Waldron, who took dramatic video of the stolen planeflying in a loop, told CNN that he was out for an evening stroll when he saw the two fighter jets following the turboprop airplane.

His first thought was that they were practicing for an air show. “So, I started to capture video, just because I thought it was kind of bizarre,” he told CNN.

Waldron said it seemed that the jets were chasing down the airplane. “I thought this is really odd. Kept the video rolling.”

Then the passenger plane pilot “did a complete loop ... I couldn’t believe he recovered.” He estimated that the plane at its lowest point was no more than 100 feet (30.5 meters) above the water. “Then the pilot “pulled - pretty much straight up. And kind of at an angle. And almost stalled the aircraft. Somehow he got it leveled back off. And then made his way down toward the island.”

Waldron said that he was prepared to “run and take cover.” He briefly turned away, then turned back and saw the explosion as the plane crashed.

- Suicide or joy ride? -

The pilot, identified as “Rich,” comes across as excitable, confused, and even apologetic in a conversation with the control tower.

“Congratulations, you did it,” the control tower tells “Rich,” according to audio that aired on CNN. “Let’s turn around the air and land it and not hurt anybody on the ground.”

“I don’t know, man,” the pilot answers. “I don’t want to. I was kind of hoping that was going to be it, you know.”

“Rich” explains that he had put some fuel in the plane “to go check out the Olympics,” but then worried that he was low on gasoline.

“I’m down to 2,100 (pounds) [952 kilos],” he says, “I don’t know what the burnage is like on takeoff, but it burned quite a bit faster than I expected.”

The control tower gently urges him to land at a nearby military base. “I wouldn’t want to do that. They probably have anti-aircraft,” he responds.

“This is probably jail time for life, huh?” he later asks, according to a recording provided by the Seattle Times. “Rich” said: “I’ve got a lot of people that care about me. It’s going to disappoint them to hear that I did this. I would like to apologise to each and every one of them. Just a broken guy, got a few screws loose, I guess. Never really knew it, until now.”

Pierce County Sheriff Paul Pastor described the incident at a press conference as a “joyride gone terribly wrong.”