PORTAGE LA PRAIRIE, Man. — Shocked passengers aboard a Greyhound bus in Manitoba said the attack was incomprehensible.

One moment, the quiet man near the back of the bus was minding his own business.

The man, believed to be in his 30s, hadn’t 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 seat-mate with a large hunting knife.

“We heard this blood-curdling scream and turned around, and the guy was standing up, stabbing this guy repeatedly, like 40 or 50 times,” Garnet Caton said Thursday from a hotel in Brandon, Man., where he and other passengers had been taken to rest.

“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.

“All very calmly. He was wearing sunglasses. It was no big deal to him.”

Fellow passenger Cody Olmstead from Kentville, N.S., also recalled the chilling scene.

“The guy came to the front of the door with buddy’s head in his hands, decapitated. He dropped the head and went back and started cutting the body back up,” Olmstead told Brandon radio station CKLQ.

Both men said the attacker and the victim appeared not to know each other.

They said the attacker boarded the bus in Brandon Wednesday night. The victim, who Caton said appeared to be about 19, had been on the bus since Edmonton.

Police didn’t confirm details, saying only that a homicide occurred on the bus, which stopped about 15 kilometres west of Portage la Prairie.

One man was taken into custody after Mounties surrounded the vehicle.

Federal Public Safety Minister Stockwell Day said the full weight of the law must be brought to bear on the perpetrator.

“We want to make sure the process is followed as aggressively as possible, the full legal process ....” Day said from Levis, Que., where Conservative MPs are gathered for a summer planning session.

“This particular incident, as horrific as it is, is obviously extremely rare. Certainly the horrific nature of it is probably one-of-a-kind in Canadian history.”

Greyhound called the event tragic but isolated.

A company spokeswoman said bus travel is the safest mode of transportation, despite the fact bus stations do not have metal detectors and other security measures used at airports.

“Due to the rural nature of our network, airport-type security is not practical. It’s a very different type of system,” Abby Wambaugh said from Greyhound’s corporate offices in Texas.

Violent incidents that have occurred on Greyhound buses in Canada

TORONTO — Here is a list of some violent attacks that have occurred on Greyhound passenger buses in Canada during the past eight years:

• July 30, 2008. Man killed and beheaded on board a Greyhound bus near Portage La Prairie, Man. Police arrest a suspect.

• Dec. 24, 2007. A 27-year-old man is stabbed after an argument with another passenger on a Greyhound bus near Tweed, Ont. A 37-year-old American man is charged with attempted murder.

• Feb. 16, 2007. A group of people in their 20’s attack and beat the driver of a Greyhound bus in Lloydminster, Alta.

• Dec. 23, 2000. A man attempts to take control of a Greyhound bus near Thunder Bay, Ont. Thirty-two passengers are injured when the bus lands on its side in a ditch. One woman later dies of her injuries.

• March, 2000. A pregnant woman is attacked by a man on a Greyhound bus in London, Ont. The woman suffered injuries to her arms.