Passengers scattered after a teen pulled out a knife and began fighting with a man on a Winnipeg Transit bus, witnesses say.

Witness Haley Musick told CBC News a teenage boy and a girl were "clearly intoxicated and super high" and causing a disturbance on the bus just after 4 p.m. Wednesday.

"They were just rambling a lot and one of them had a knife," she said.

Haley Musick says she wishes she had taken the Route 65 bus instead of being on the one with all of the chaos. (John Einarson/CBC)

Another passenger, a man Musick said was a security guard, tried to defuse the situation, but the teens started attacking him, hitting and scratching him, she said.

"He had two black eyes. It was just awful looking," she said.

The man got the knife away from the teen and gave it to the bus driver, said police, who were called when the bus pulled over to the curb near Osborne Street and York Avenue and all the other passengers got off.

"Then the police came and they started attacking them," Musick said, lamenting her choice of bus routes that day.

"I should have taken the 65."

Police speak to a witness after the bus incident on Wednesday afternoon. (John Einarson/CBC)

The teen girl jumped on the back of the the security guard, who was trying to help police officers, and scratched at his face, police said.

The officers eventually gained control and arrested the teens, but not before the girl spat in the face of one officer.

Both teens are now in custody and facing charges.