The Arizona helicopter crash that killed five passengers — including former Islanders businessman Tom Stewart and pilot John “Rick” Morton — was caused by a rotor blade flying apart, according to a lawsuit filed last week by pilot Morton’s family.

The aircraft that crashed was multimillionaire Stewart’s personal helicopter, and one of its rotor blades had been repeatedly repaired, attorney Gary C. Robb told the Associated Press (AP) last week. Robb filed a lawsuit against the helicopter’s manufacturer and mechanic on behalf of Morton’s wife and adult daughter, both of the Seattle area.

Though the official cause of the Feb. 14, 2010, accident has not yet been determined, some had believed mechanical failure was to blame because eyewitnesses reported seeing parts fly off the copter just before it crashed, according to the AP.

Morton, 63, was a former Vashon resident who lived on the Island for years while working as Stewart’s personal pilot before relocating with Stewart to Arizona when the food service magnate moved there in 2006. A U.S. Army veteran, Morton served in Vietnam and had put in more than 11,000 flight hours in 30 years, according to AP. It was his 38th wedding anniversary on Feb. 14, 2010, the day Stewart’s helicopter crashed and killed all five aboard.