Officials identify remains of Seattle plane thief as 29-year-old Richard Russell

Authorities have identified the remains of the 29-year-old who stole a commercial airplane that took off from Sea-Tac International Airport and crashed into a small island in Puget Sound Friday evening.

The FBI located Richard Russell's remains and the Pierce County Medical Examiner’s Office confirmed the identification on Monday.

The flight data recorder and the cockpit voice recorder from aircraft N449QX was also recovered. The National Transportation Security Board is processing the data.

While authorities are still conducting search and wreckage recovery efforts, the FBI said it has no reason to believe anyone else was in the aircraft.

Russell’s motive behind stealing the aircraft is still unclear. He could be heard on audio recordings telling air traffic controllers that he is "just a broken guy." His family says it's clear he didn't mean to harm anyone.

In a written statement to the media on Saturday, Russell's family described him as a faithful husband, loving son and a good friend who didn’t mean to harm anyone.

The investigation is ongoing and the FBI is interviewing relevant airline and airport personnel, as well as gathering video and communications related to the incident, an agency spokesman said.

Video showed the Horizon Air Q400, a turboprop plane that seats 76 people, doing large loops and other dangerous maneuvers as the sun set on Puget Sound Friday evening.

Investigators are trying to determine how the 3 1/2-year Horizon employee, who had clearance to be among aircraft, but that to their knowledge, wasn’t a licensed pilot, had attained the skill to perform such dangerous maneuvers.

Erroll Southers, a former FBI agent and transportation security expert, said if he was capable of performing “loops with a plane like this, he certainly had the capacity to fly it into a building and kill people on the ground.”

The flight lasted about 75 minutes before the plane crashed into the tiny Ketron Island, southwest of Tacoma, Washington after being chased by military jets.

Fox News’ Edmund DeMarche and Frank Miles contributed to this report.