He is accused of one of the most gruesome crimes of recent years – decapitating and cannibalising another passenger on board a Greyhound bus – but when Vince Weiguang Li appeared in a Canadian courtroom on Tuesday he gave no reason for the attack, uttering just three words: “Please kill me”.

Li, who immigrated to Canada from China in 2004, is accused of killing 22-year-old carnival worker Tim McLean in front of fellow passengers on a Greyhound bus which was travelling along a remote highway from Edmonton, Alberta, to Winnipeg, Manitoba, last Wednesday night. He is charged with second degree murder.

Appearing in court in Manitoba yesterday, Li, 40, was ordered to undergo a psychiatric evaluation as prosecutors revealed that he had a plastic bag containing his victim's ear, nose and part of a mouth in his pocket when police officers arrested him.

Prosecutor Joyce Dalmyn said Li, who was armed with a pair of scissors, was seen by officers “cutting body parts from the victim and eating those body parts” and had carried the victim's severed head back and forth on the bus “taunting” officers.

She said the only response police received from Li when they approached him was: “I have to stay on the bus forever”.

Ms Dalmyn said that in an interview with police after his arrest Li had declined to speak for the most part but on four occasions had indicated in a low voice that he was guilty.

The gruesome and apparently unprovoked murder occurred while some of the 37 passengers slept and others watched the movie The Legend of Zorro as the bus travelled along a desolate stretch of the TransCanada Highway.

Horrified passengers fled the bus as Li began stabbing McLean, who was sitting next to him and was said to be sleeping and wearing headphones when he was attacked.

Witnesses said Li then severed McLean’s head and displayed it to some of the passengers outside the bus before he began hacking at the body.

According to a leaked police tape, one officer at the scene reported seeing Li cutting off pieces of the victim's body and eating them.

Ms Dalmyn said police are looking into information that Li may have spent as many as four days in a psychiatric facility prior to the attack.

However a church pastor who hired Li when he first immigrated to Canada with his wife, Anna, said that he had never showed any signs of anger or emotional problems when he worked there as a custodian.

Since his arrest, Li has declined to speak to prosecutors and his court-appointed attorney.

Instead, when asked by Provincial Court of Manitoba Judge Michel Chartier if he wanted a lawyer, Li shook his head and quietly said: “please kill me”.

Ms Dalmyn said Li is due back in court September 8 when prosecutors hope he will have had a psychiatric assessment.

“Then we can look to consider whether in the psychiatrists opinion the accused is fit to stand trial and whether we are proceeding at that point or whether there are fitness concerns that need to be canvassed by the court,” she said.

In the wake of the attack, Greyhound has scrapped a billboard ad campaign that extolled the relaxing upside of bus travel which had the unfortunate punch line stating: “There's a reason you've never heard of 'bus rage’”.

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