(Seattle, WA) -- An investigation is ongoing into a bizarre passenger plane theft in Washington State. The 76-seat Horizon Air plane was stolen by an employee Friday night. Sitting in the cockpit, 29-year-old Richard Russell communicated with air traffic control and performed some stunts in the air before crashing on an island in the Puget Sound. No one else was believed to be on board, but military jets were scrambled out of Portland to intercept him. The FBI says it recovered the flight data recorder and parts of the cockpit voice recorder from the plane over the weekend, along with human remains believed to be that of Russell.