Most horrific detail about Greyhound bus killing...

On Wednesday, a 40-year-old man suddenly attacked, stabbed and decapitated a fellow passenger on a Greyhound bus traveling across Canada.

One of the 37 passengers told Canadian television: "All of a sudden, we all heard this scream, this bloodcurdling scream. 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.

"There was no rage in him," added the witness of the killer. "It was just like he was a robot or something."

Passengers fled the bus for the Canadian prairie outside and also held the bus doors shut when the killer charged at them. Authorities apprehended the man after a long stand-off, but as of this writing no charges have yet been filed.

The victim is described as a 20-year-old man who was listening to headphones before being attacked. Neither the killer nor the victim have been identified.

More from the BBC here.