An Amtrak police officer has been charged with first-degree murder in the shooting death of a 25-year-old Minnesota man outside Union Station last week.

LaRoyce Tankson, 31, turned himself into law enforcement authorities late Thursday, according to the Cook County State's Attorney's office. He was charged in connection with the fatal shooting of Chad Robertson.

Robertson died Wednesday at Stroger Hospital, one week after being shot near Jackson and Canal.

His death came a day after a federal lawsuit was filed on his behalf against the rail agency and the officer who shot him.

Chicago Police have said Robertson was unarmed.

"Amtrak continues to cooperate fully with the Chicago Police Department and State’s Attorney’s office," the transit agency said in a statement Friday. "As this matter is ongoing, we are unable to comment further."

The two officers involved were reassigned to desk duty per Amtrak policy following the shooting, spokesman Marc Magliari said.

“Amtrak is deeply saddened to learn of the passing of Chad Robertson,” Magliari said. “Amtrak is cooperating fully with the Chicago Police Department and State’s Attorney’s office as they conduct an independent investigation.”

During an hourlong layover on a Megabus trip from Memphis to Robertson’s hometown of Minneapolis, the officers were “aggressive” when they walked up to him and two other riders inside Union Station, before following them as they walked outside to a restaurant, the suit says.

The officers stopped them again and started searching them, the suit says. Robertson “feared for his life” and started running.

One officer “calmly dropped to one knee, removed his gloves, unsecured his weapon” and fired a shot from about 30 feet away that missed, according to the suit, which says the second shot hit Robertson in the back. He was taken to Stroger Hospital in critical condition.

The officer gave no commands but “calmly stated, ‘It’s a gun out. It’s a gun out,'” the suit says.

Chicago Police said Robertson was shot in the shoulder and that he was carrying cash and drugs. His attorney said he had “an insignificant” amount of marijuana, and that the father of two has no criminal record.

Doctors weren’t able to remove the bullet from Robertson’s spine, who was left quadriplegic in his final days, the suit says.

“When he found out about his condition from the doctors, he was heartbroken,” his sister, Nina Robertson, said at a press conference last week. “He just said, ‘The police ruined my life.’”

Magliari said Amtrak would review the suit but declined to comment Wednesday night. Chicago Police had no updates on the investigation.

Robertson’s family said his two companions who witnessed the shooting were set to appear before a grand jury last week. Representatives for the Cook County state’s attorney’s office declined to comment.

An autopsy on Robertson was scheduled for Thursday.

The nine-count civil rights suit claims the officers used excessive force and searched Robertson illegally. The suit is seeking an unspecified amount in damages.