The mental state of a 44-year-old Michigan man charged with attempted murder in the stabbing of three other passengers and a conductor on an Amtrak train will be looked into by detectives investigating the case.

Niles Police Chief Jim Millin says Sunday that detectives have spoken with Michael Williams and "have a little better understanding of how" Friday night's attack went.

Millin could not discuss a motive in the stabbings, but adds there is nothing to indicate Williams had any previous relationships with the victims who were in stable condition Sunday.

They were stabbed while the train was stopped in Niles. It was headed to Port Huron from Chicago.

Officers used a Taser to subdue Williams on the train. He is jailed and faces an initial court appearance Monday.