A male passenger in his 20s was stabbed repeatedly and later decapitated by another male in his 40s while traveling on a bus in Canada's Manitoba province, police and witnesses said Thursday.

A male passenger in his 20s was stabbed repeatedly and later decapitated by another male in his 40s while traveling on a bus in Canada's Manitoba province, police and witnesses said Thursday.(Xinhua/Reuters Photo)

The gruesome event happened around 8:30 p.m. Wednesday local time on an eastbound Greyhound bus on the Trans-Canada Highway about 20 kilometers west of the city of Portage la Prairie. The bus was carrying 37 passengers and the driver to provincial city Winnipeg from neighboring Alberta province.

Royal Canadian Mounted Police (RCMP) officers confirmed Thursday that a male suspect is in custody and investigation is going on, but they did not disclose any details.

Shocked passengers described the horrific attack as something incomprehensible. They say the man repeatedly stabbed his seat-mate before beheading him and carrying the victim's head around the bus.

According to witnesses, one moment, the quiet man near the back of the bus was minding his own business. He had not talked to anyone around him, and seemed to pay no attention to the younger fellow sitting next to him, who was listening to music on headphones.

The next moment, witnesses said, the older man stood up, still quiet, and repeatedly stabbed, then beheaded his younger victim.

"We heard this blood-curdling scream and turned around, and the guy was standing up, stabbing this guy repeatedly, like 40 or 50 times," a witness named Garnet Caton said.

"There was no rage or anything. He was like a robot, stabbing the guy."

Caton said the bus stopped and everyone scrambled to get out while the attacker started methodically carving up the victim's body, not paying attention to anyone else.

Caton and the driver shut the bus door from the outside while they waited for police to arrive.

"We put our bodies up against the door, waiting for him to come out ... and he went back and brought the head to the front and pretty much displayed it ... and dropped it on the ground in front of us," Caton said.

When police arrived, the victim and his attacker were the only ones left on the bus. The man eventually tried to flee by breaking a bus window and jumping out, but he was immediately subdued and arrested without incident.

Police say they have no clues as to what prompted the attack. Witnesses say the attacker and the victim did not seem to know each other.