Russell's heartbreaking exchange with air traffic controllers ― who called him "Rich" ― was broadcast live and could be heard online.
The air controller tells him there is a runway just off to his right "in about a mile [1.6km]", referring to a military airfield at Joint Base Lewis-McChord.
"Got a few screws loose, I guess", he is heard saying in the recording.
"Doing stunts in air or lack of flying skills caused crash into Island", the sheriff said on Twitter.
F-15 fighter planes were sent to intercept the aircraft, but were not involved in the crash, said the Pierce County Sheriff's Department.
Alaska Airlines and Horizon Air officials said they were still working closely with authorities to investigate what happened.
Alaska Airlines executives said at a news conference at Sea-Tac late Saturday morning that the employee who took the plane was authorized to be both on the tarmac and inside planes and that not security protocols were violated.
A passenger plane from Alaska Airlines was stolen from Seattle-Tacoma International Airport on Friday at around 8 PM.
Authorities say Richard Russell stole a Horizon Q400 aircraft and took it to the air later resulting in the loss of his life following a crash into an island.More news: Scientists concerned about endangered orca still pushing body of her calf
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Investigators from the National Transportation Safety Board, the Federal Bureau of Investigation and Alaska Airlines were headed to Ketron Island on Saturday morning to gather evidence from the site where a Horizon employee crashed a stolen airplane.
The Pierce County sheriff said that the perpetrator acted alone and "was confirmed a suicidal male". The plane was "highly fragmented and the wings are off", she said. "I've played some video games before", he said.
On a SoundCloud site, Russell interviews fellow ground service agents, asking them questions that include: "What was one of your best travel experiences using your flight benefits?"
NBC reported that the man expressed distress about his mental health while communicating with the air traffic control tower.
The wooded area is hard to access, and because there are no fire engines on the island, everything has to get to there via ferry, Adams said.
He then said: "I wouldn't know how to land - I wasn't really planning on landing it".
The plane was pursued by military aircraft before it crashed on tiny Ketron Island, southwest of Tacoma, Washington. The man was a ground service agent, a job that includes directing aircraft for takeoff and gate approach, handling baggage and de-icing planes, authorities said.
A "suicidal" airline mechanic stole an empty plane before flying around an airport then crashing near a small island. "But holy smokes, I got to stop looking at the fuel, because it's going down quick". At that speed, the F-15s could have reached the Q400 in less than five minutes after take off from Portland.