MAN DECAPITATED ON CANADIAN BUS !
An eyewitness said the victim was stabbed 50 or 60 times by the man sitting next to him, who then severed his head with a large knife.
The bus made an emergency stop to allow passengers to escape and the driver barred the door from the outside while waiting for the police to arrive.
The bus was travelling from Edmonton, Alberta, to Winnipeg, Manitoba.
Greyhound Canada said there were 37 passengers and a driver aboard the bus.
"All of a sudden, we all heard this scream, this bloodcurdling scream," passenger Garnet Caton told CBC television.
"The attacker was standing up right over the top of the guy with a large hunting knife - a survival, Rambo knife - holding the guy and continually stabbing him... in the chest area," Mr Caton added.
The attack continued as passengers fled the bus and waited for police on a desolated stretch of the TransCanada Highway near Portage la Prairie, Manitoba.
"He calmly walks up to the front [of the bus] with the head in his hand and the knife and just calmly stares at us and drops the head right in front of us," Mr Caton said.
"There was no rage in him ... It was just like he was a robot or something," he added.
A man was taken into custody by police at around 0100 (0700 GMT) on Wednesday night, according to reports.
Mr Caton said he and a truck driver helped the bus driver bar the bus door to prevent the attacker from leaving.
When the attacker tried to drive the bus away, the driver disabled the vehicle.
"Some people were puking, some people were crying, other people were in shock ... everybody was running, screaming off the bus," Mr Caton said.
The Royal Canadian Mounted Police said only that a "major incident" took place on the bus as it drove along the Trans-Canada Highway en route to Winnipeg from Edmonton.
Other passengers said that the attacker and his victim were sitting at the back of the bus and the victim, described as around 20 years old, was listening to music through headphones.
The attack appeared to be unprovoked and it is thought the killer did not know his victim.