July 31 (Bloomberg) -- A young man was stabbed and then beheaded in what appears to be an unprovoked attack on a Greyhound bus in the Canadian province of Manitoba, en route to Winnipeg.

The attack occurred last night west of Portage la Prairie, Manitoba, in a bus traveling from Edmonton, Alberta.

Authorities have arrested a suspect, Royal Canadian Mounted Police Staff Sgt. Steve Colwell said today in a televised news conference from Winnipeg, the provincial capital. The victim's identity won't be released until his family is notified, Colwell said.

The victim was about 18, and had been sleeping with headphones on when he was attacked, according to a report on the Web site of the Globe and Mail newspaper.

Police arrived just after 8:30 p.m. and arrested a man following a standoff around 1:30 a.m. when he broke through a window and tried to jump off the bus, Colwell said. The bus stopped on the Trans Canada Highway after the attack, and the driver and 34 passengers rushed off; the Globe report said they held the door closed to keep the attacker inside.

``The way they reacted was extraordinary,'' Colwell said. He said the arrested man, who is 40, had not yet been charged and police were talking to prosecutors about how to proceed.

The victim had been asleep when his seat mate suddenly began stabbing him in the throat with a hunting knife, according to a passenger sitting in the seat in front of them, the Globe and Mail said. The attacker then cut off the victim's head and carried it to the front of the bus after the other passengers had rushed off, the newspaper said.

Stockwell Day, federal public safety minister, described the event as ``probably one of a kind in Canadian history.'' Day told reporters at a meeting of members of the ruling Conservative Party in Levis, Quebec, that ``we want to make sure that the process is followed as aggressively as possible, the full legal process.''

To contact the reporter on this story: Greg Quinn in Ottawa at gquinn1@bloomberg.net.

Last Updated: July 31, 2008 17:38 EDT