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A man who stabbed four people on an Amtrak train in Michigan, including a conductor, was apprehended Friday night, police said. Michael Darnell Williams, 44, was charged with four counts of assault and intent to murder, Niles Police Chief Jim Millin told NBC News. Williams is being held on $1 million bail, according to NBC Chicago.

The suspect first boarded the train in Chicago. Michigan police responded to a call from Amtrak Chicago around 7 p.m. advising they had a man on the train who was "talking to himself, acting strangely and acting agitated," Millin said at a news conference Friday. When police arrived at the train when it was stopped near Niles, north of South Bend, Indiana, the knife attack was already taking place. Officers rushed onto the train and shot the suspect with a Taser before arresting him.

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One female, two male passengers and a male conductor were injured during the stabbing spree, Millin said. One victim was in serious condition after being stabbed in the chest area, he added.

Police said the suspect was traveling alone and did not release a motive for the assault. A bystander told WNDU that the man first attacked a male passenger before going after the female victim.

"I was like 'Oh my God, he's punching the guy. I saw him bring his fist back up and I noticed there was something in his fist resembling a knife blade and bring it back down," the passenger on the train from Chicago to Port Huron, Michigan, told NBC affiliate WNDU.

Amtrak said in a statement that they were assisting in the investigation and would find alternate transportation for the 172 passengers on the train.

SOCIAL

Here's mugshot of Michael Darnell Williams - facing 4 counts of assault with intent to murder after Niles stabbing. pic.twitter.com/cEgX9BnTz6 — Gabby Gonzalez (@Gabby_Gonzalez) December 6, 2014

This is a picture of the suspect in handcuffs after multiple people have been stabbed on an Amtrak train in Niles. pic.twitter.com/JOyqwDaf3x — WNDU (@WNDU) December 6, 2014

— Daniella Silva, Elisha Fieldstadt and Phil Helsel