Bail has been set at $1 million for a man accused of stabbing four people on an Amtrak train that was leaving Chicago Friday.

NBC Washington reported Michael Darnell Williams, 44, was originally arrested on charges of assault with intent to murder for his actions on the train that departed from Chicago and was en route to Port Huron, Michigan.

But the family of Williams, who had been traveling alone from Saginaw, Michigan, told the Chicago Tribune that he was an army veteran and had been suffering mental issues.

Police were first made aware of the situation on board the train when several callers reported a suspicious individual at about 7 p.m. Friday.

By the time police arrived, the attack was already under way, NBC reported.

Williams' grandmother, Ethel Williams, 89, said he had served in the U.S. Army for 10 years and had previously been at a Veteran's Affairs hospital before being released and prescribed medication.

"I know one thing, he needs to be in a hospital, there's something wrong with him. I don't know what it is, but there's something wrong with him," Ethel said. "He's supposed to be taking some kind of medicine. They gave him some medicine."

She said he was on his way back to Saginaw and that it was likely that he did not board the train in Chicago.

Williams is accused of stabbing a female and three males, according to the Niles, Michigan, police. The train was in Niles when police got on board.

The four victims were taken to area hospitals and are reportedly in stable condition. The investigation is ongoing, but Williams is scheduled for a video arraignment on Monday.

His grandmother said the incident may have erupted from someone bothering him.

"I know he needs to be back in the hospital where those veterans are at," she said. "Someone told me that he thought someone was bothering him."