Four people were stabbed on an Amtrak train from Chicago to Port Huron, Michigan.
It happened at 6 p.m. Chicago time on Friday, as the train pulled into the station in Niles, in Southwest Michigan near South Bend, Indiana.
Police met the train at the station after the conductor called to report a passenger who was acting erratically.
While the train was stopped, the man pulled out a knife and started stabbing people ... including the conductor. Two of the victims were rushed into surgery.
Police say they used a stun gun to subdue the man after he threatened officers with the knife. He was arrested, but charges are still pending.
The train was stopped in Niles for several hours, while police conducted their investigation.
The suspect is a 44-year-old from Saginaw, Michigan, according to a CNN affiliate.
It's unclear what his motive was.