The sheriff's department tweeted that there were no passengers on plane.
The airport confirmed the airplane theft, in a statement: "An airline employee conducted an unauthorized takeoff without passengers at Sea-Tac; aircraft has crashed in south Puget Sound". The joyride came to an end when he crashed the plane into Ketron Island, a small island southwest of Tacoma. "Was doing stunts in air or lack of flying skills caused crash into Island", the sheriff's office tweeted.
Officials said the 29-year-old man who stole the plane was "suicidal" and there is no connection to terrorism.
Alaska Airlines said it "believes" the man was a ground service agent working for Horizon Air.
Earlier, Alaska Airlines, the parent company of Horizon Air whose plane was stolen, tweeted a statement.
The man could reportedly be heard on audio recordings telling air traffic controllers that he is "just a broken guy".
Instead, police described the man as "suicidal" who experienced "emotional distress" when communicating with air traffic controllers.
The man responded: "Awwww-right. dammit".
"I'm not quite ready to bring it down just yet", the pilot says. I don't know! I don't want to. "So, I started to capture video, just because I thought it was, kind of freaky", he told CNN. It did not elaborate.
Two military F-15s were scrambled to chase the stolen plane, but officials said the jets were not involved in the crash. They pursued the aircraft before it went down on Ketron Island between Tacoma and Olympia.
Remains of boy found at New Mexico compound
Taos county deputies found 11 children, ranging in age from 1 to 15 in unhealthy conditions at the makeshift compound in Amalia. What authorities found was what Hogrefe called "the saddest living conditions and poverty " he has seen in 30 years on the job.
Only the unknown pilot was on the plane. The jets were not involved in the crash, it said.
The governor of Washington, Jay Inslee, thanked the Air National Guard from Washington and OR on Twitter "for scrambling jets to keep Washingtonians safe".
The airport also confirmed the plane wasn't carrying passengers.
Waldron said it seemed that the jets were chasing down the aeroplane.
At another point, Rich said, "I've got a lot of people that care about me".
Reporter Austin Jenkins of Northwest News Network circled Ketron Island, the site of the crash landing, by boat Friday night.
"Everyone was literally frozen in place muttering about what possibly happened", he said.
Two F-15s and air traffic control operators helped steer the plane away from built up areas and out over the water before it crashed.
Video from the scene shows the plane, which had no passengers on board, fly upside down while being tracked by fighter jets.