A policeman photographs the scene around a Greyhound bus about 20 km (12 miles) west of Portage la Prairie, July 31, 2008. A 40-year-old man was charged on Friday with second degree murder after a fellow passenger was stabbed to death aboard a Greyhound bus on the Canadian Prairies and then beheaded. REUTERS/Fred Greenslade

WINNIPEG, Manitoba (Reuters) - A 40-year-old man was charged on Friday with second degree murder after a fellow passenger was stabbed to death aboard a Greyhound bus on the Canadian Prairies and then beheaded.

The killing occurred on Wednesday as the Greyhound moved east on the TransCanada Highway near Portage la Prairie, Manitoba, and the gruesomeness of the death sent shock waves across the country.

The Royal Canadian Mounted Police said Vince Weiguang Li of Edmonton, Alberta, has been charged with second degree murder.

Li looked down during his first court appearance on Friday, nodding his head when asked whether he was using his right to remain silent, according to media reports from Portage la Prairie, a small city about an hour’s drive west of the Winnipeg.

Police have not speculated on a motive, but the charge of second degree murder is usually filed when police do not believe the killer planned the murder or targeted the victim in advance.

Witnesses have said that the killer, who brandished a “Rambo”-style hunting knife, did not appear to know the sleeping victim and that the attack began without warning.

The attorney prosecuting the murder charge asked that Li have a psychiatric assessment, but the judge said Li would first need to get a lawyer, the Canadian Broadcasting Corp said.

If evidence shows the attacker was mentally ill and did not understand what he was doing, criminal charges may not stand up, Fred Shane, a Manitoba forensic psychiatrist, told Reuters.

Friends told local media the victim was Tim McLean, 22, who had been working at a carnival in Edmonton before returning to his Winnipeg home. Police have not confirmed this.