Passenger decapitated on Greyhound bus.

A 40-year-old man is in custody in Manitoba after a young man was stabbed — and, witnesses said, decapitated — aboard a Greyhound bus travelling through the province overnight.

Thirty-seven people were aboard the bus en route to Winnipeg from Edmonton. Colwell said the "brave" behaviour of the passengers and driver probably prevented anyone else from being hurt.

Garnet Caton, who was sitting in the seat in front of the victim, said he saw the attacker stab his seatmate, a young man sleeping with his headphones on. Caton said he heard a "blood-curdling scream" and turned around to see the attacker holding a large "Rambo" hunting knife above the victim, "continually stabbing him in the chest area."

"He must have stabbed him 50 times or 60 times," said Caton. "Like, just everywhere, arms, legs, neck, chest, guts, wherever he could swing it, he got it," said Olmstead.