Passengers at Seattle-Tacoma International Airport, which claims to be the ninth busiest United States airport took to Twitter to vent their frustration after the incident grounded all flights for up to any hour.
"We believe there are no passengers on board", the tweet said.
Witnesses reported seeing the plane being chased by military aircraft before it crashed near Ketron Island.
Tonight, a 29-year-old mechanic from an unknown airline stole a Horizon Airlines plane from SeaTac Airport in Seattle, according to the Pierce County Sheriff's Office.
Earlier, Alaska Airlines, the parent company of Horizon Air whose plane was stolen, tweeted a statement.
The Q400 is a 76-seater turboprop aircraft.
Video showed the Horizon Air Q400 doing large loops and other unsafe manoeuvres as the sun set on the Puget Sound.
The man was a resident of Pierce County, Wash., and "acted alone", the Pierce County Sheriff's Department tweeted.
FBI Seattle announced on Twitter it would work with local authorities to investigate the accident but said evidence does "not suggest a terrorist threat".
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The Pierce County Sheriff's Department has a number of vessels on scene, while the U.S. Coast Guard is on scene as well.
The video then ends - and just moments later the aircraft had crashed in the Pudget Sound.
The plane, a Bombardier Dash 8 - Q400, has the capability to hold about 75 passengers and is used for short travel in the West.
Witnesses said a. plane is going down.
Two F-15 fighters were scrambled and all SeaTac flights were briefly grounded, the Tacoma News Tribune reported.
There was no indication that the incident was an act of terror and no passengers were aboard the plane, the Federal Bureau of Investigation said in a series of Tweets.
The man could be heard on audio recordings telling air traffic controllers he is "just a broken guy".
Royal King of Mukilteo was photographing a wedding at Lake Steilacoom when he saw the low-flying plane and two fighter jets trailing it.
Jenkins described the island as remote, dark and sparsely populated. He said he didn't see the crash but saw smoke.
This story is still developing....