A man sleeping on a Greyhound bus as it rolled across the Canadian Prairies was killed and decapitated by his seatmate on Wednesday night, other passengers who were on the bus told media on Thursday, Reuters reported. "All of a sudden, we all heard this scream, this bloodcurdling scream," said Garnet Caton, who was sitting just in front of the victim, in an interview with CBC Television. "The attacker was standing up right over top of the guy with a large hunting knife -- a survival, Rambo knife -- holding the guy and continually stabbing him, stabbing him, stabbing him in the chest area," Caton said. The attack continued as other passengers fled the bus and waited for police on a desolated stretch of the TransCanada Highway near Portage la Prairie, Manitoba, said Caton, who helped bar the bus door to prevent the attacker from leaving. "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," Caton said.