A federal grand jury in Brooklyn has returned a two-count indictment against alleged subway shooter Frank James

The indictment expands the charges James is facing for allegedly shooting 10 people on a Manhattan-bound N train on April 12. No one was killed.

James is now charged with carrying out a terror attack against a mass transit system and discharging a firearm during a crime of violence.

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If convicted of the terror charge, he faces up to life in prison. The second charge also carries the possibility of a life sentence.

No date was set for his arraignment.

The shooting during the Tuesday morning commute set off a 24-hour search for the gunman. The following day, several callers to the New York Police Department tipline said a man matching the description of the shooter was wandering around the Lower East Side and East Village.

James himself was one of those people police believe called into the tipline. The caller claimed police were looking for him and he'd be waiting at a McDonald's at Sixth Street and First Avenue. Police responded to the area and James was arrested without incident a short time later.

MORE: Timeline of New York subway shooting and capture of suspect

James did not enter a plea in his first court appearance on April 14. Following the appearance, his lawyer, Mia Eisner-Grynberg, called the shooting a tragedy but said that initial information can often be wrong. She also lauded James for turning himself in.

He is being held without bail. A motive for the attack remains unclear.

ABC News' Mark Osborne contributed to this report.