Police officers struggling to get through a chaotic scene aboard an Amtrak train in Michigan are being credited with preventing even more bloodshed after a man stabbed a conductor and three fellow passengers.

"It was pretty incredible that they may have saved some lives," passenger Tyler Vandermolen said.

Michael Williams, 44, of Saginaw was charged Saturday with attempted murder. He's accused of stabbing four people while the train was stopped Friday night at a depot in Niles in southwestern Michigan, about 10 miles north of South Bend, Indiana. The victims were reported to be in stable condition.

Officers rushed to the scene after Amtrak called police about a passenger acting suspiciously on the Chicago-to-Port Huron train, Niles Police Chief Jim Millin said.

"They saw commotion in the train car," Millin said of his officers. "They had to forcefully work their way through the crowd. As soon as the first officer turned into the car, Mr. Williams was less than 10 feet away and he had the knife in his hand. The officer used his Taser and was able to subdue" him.

"Certainly there's a possibility he could have kept on assaulting passengers and things could have been a lot worse," the chief told The Associated Press.

The motive wasn't known. Williams was being held on $1 million bond Saturday at the Berrien County jail and his initial court appearance was scheduled for Monday.

"It doesn't appear he was screaming or in anger against any of these people. He just started cutting and stabbing," Millin said.

Niles Mayor Michael McCauslin said the wounded included a train conductor, a female passenger and two male passengers.

The train, which had been carrying 172 passengers, remained in Niles for hours after the attack while investigators gathered evidence and spoke to witnesses. It finally resumed its journey at 1:20 a.m. Saturday.

Passenger Caitlin Cipri told the South Bend Tribune that she was packing her things to get off the train when she heard screaming. She initially thought the suspect was punching a passenger until she saw the butt of a knife. She said she saw the man stab two other people.

"It was terrifying and you don't think something like that is going to happen to you," Cipri said. "It's terrifying that things like this happen."

Online records show Williams had a drug conviction in Saginaw County in 1997.