One of the first police officers on the scene of the beheading of a young man aboard a Greyhound bus on a Manitoba highway six years ago has taken his own life.

Ken Barker, a recently retired RCMP corporal who was a dog handler, killed himself last weekend after struggling with post-traumatic stress disorder for years, Winnipeg Free Press reports.

Family and former colleagues say the 51-year-old had already seen almost two decades of horrific crimes when he witnessed the grisly scene on the Trans-Canada Highway west of Winnipeg in 2008.

Tim McLean was stabbed, mutilated and beheaded by Vince Li, who was later found not criminally responsible because of mental illness.

Barker’s family say they’re speaking out about the suicide in the hope more Mounties will seek help.