The NYC subway shooting suspect has been indicted by a grand jury on a federal terror charge

• A federal grand jury returned an indictment against NYC subway shooting suspect Frank James.
• The indictment was unsealed on Saturday and includes a federal terror charge.

A federal grand jury has indicted New York City subway shooting suspect Frank James, who is accused of opening fire on a crowded N train and injuring 10 people last month.

The grand jury charged James, 62, with carrying out a terror attack against a mass transit system and discharging a firearm during a crime of violence. The grand jury handed down the indictment on Friday, according to the Associated Press, but it wasn't unsealed until Saturday.

Authorities said James boarded a busy N train during rush hour on the morning of April 12, detonated smoke grenades, and opened fire as the train pulled into Brooklyn's 36th Street subway station.

Police arrested James some 30 hours after the attack, following a massive, city-wide manhunt. During James' first appearance in Brooklyn federal court on April 14, a federal prosecutor told the judge that James' alleged attack created terror "that the city has not seen in more than 20 years."

The motive for the April 12 attack remains unclear, but in the years leading up to the attack, James had uploaded more than 400 videos to a YouTube account rife with bigoted rants and conspiracy theories, Insider's Haven Orecchio-Egresitz previously reported.

One video he uploaded exactly one month before the shooting included racist statements against Spanish speakers and Latinos. James also spoke in the video about his diagnosed mental illness.

James is currently being held without bail in Brooklyn's Metropolitan Detention Center. He faces up to life in prison if convicted of the terror charge. Federal court documents listed no date for James' arraignment.

Also on Friday, a US magistrate judge denied one of James' motions that sought the release of documents and affidavits related to a DNA cheek swab conducted on April 26. The judge's order noted that the motion was moot, since federal prosecutors had already provided an affidavit and never asked James to sign documents while the search warrant for the cheek swab was executed.