This is a developing story, more information to come.
The FBI is leading the probe, which also includes the Federal Aviation Administration and the National Transportation Safety Board.
Investigators would not name the employee who took the plane, but in a statement read by a family friend on Saturday night, the family confirmed it was Russell, who was married and lived in Sumner, Washington.
"This is going to take a little bit of time", said Jay Tabb, special agent in charge of the bureau's Seattle Division.
The incident fell under the ongoing mission of Noble Eagle, the air-defense mission launched after the 9/11 terrorist attacks, Hillier said.
Astonishing video showed the Horizon Air Q400 doing large loops and other risky manoeuvres. There were no passengers aboard.
Troyer said the man who stole the plane is a mechanic at the airport.
"It may seem hard for those watching at home to believe, but Beebo was a warm, compassionate man", the statement said.
Gary Beck, CEO of Horizon Air, told reporters that "to our knowlege, he didn´t have a pilot´s license".
"I don't know man", Rich said.
Royal King, a Seattle-area resident in the area to photograph a wedding, was near the island when the plane cratered into the island, the Times reported. Video showed fiery flames amidst trees on the island, which is sparsely populated and only accessible by ferry.
And there was no indication that the incident was an act of terror, Pierce County Sheriff Paul Pastor told KIRO7 news station in Seattle.
They may have cost him his life, but an airline employee's acrobatics in an empty propeller plane he stole in Seattle drew words of wonder from the head of the company where he'd worked.
In a statement to PEOPLE, Alaska Airlines said, "We are aware of an incident involving an unauthorized take-off of a Horizon Air Q400". The plane involved was a Horizon Air Q400 with no passengers on board, tweeted Alaskan Airlines.
Kaelin said it has been painful for him to hear reports with audio of Russell's conversations with air traffic control during the flight that ended with him crashing on Ketron Island, about 25 miles southwest of where he took off.
The "suicidal" man who commandeered and crashed a plane without passengers from a USA airport in Washington state seemed excited, confused, and at times calm while talking with the air traffic control tower.
Scott Adams, a battalion chief with West Pierce Fire and Rescue, said about 10:30 p.m. the crash had started a grass fire, and that two fire engines, a medic unit and a command unit were at the site, along with firefighting staff from Joint Base Lewis-McChord. The man sounds calm at times and jokes with operators on the ground, who try to direct him to places to land.
Communication between the hijacker and Air Traffic Control- "I've got a lot of people that care about me".
At one point, he said: "Hey do you think if I land this successfully Alaska will give me a job as a pilot?"
"Got a few screws loose, I guess", he is heard saying in the recording.
Alaska Airlines said the plane was in a "maintenance position" when it was stolen and not scheduled for a passenger flight. The crash sparked a 2-acre wildfire. The plane was "highly fragmented and the wings are off", she said.
White House Press Secretary Sarah Huckabee Sanders said Saturday morning that President Donald Trump is "monitoring the situation".