A grand jury in New Haven on Wednesday returned a one count indictment charging a former New London man with being a felon in possession of ammunition.

West “Po,” Robertson, 31, of Norwich initially was arrested Monday on a federal complaint after authorities said he was found on May 29 to be in possession of seven .40 caliber Smith & Wesson shell casings.

New London police said they assisted the Bureau of Alcohol, Tobacco, Firearms and Explosives in an investigation into Robertson’s connection with the May 29 shooting in the area of Alger Street and Riverview Avenue. A man was shot multiple times in the incident.

Details of the investigation remain sealed by a court order, according to a spokesman with the U.S. Attorney’s Office.

The charge against Robertson carries a maximum of 10 years in prison but he could face from 15 years to life if convicted and subjected to the Armed Career Criminal Act, a federal law imposing severe penalties for firearm and ammunition possession by persons who have been convicted of at least three violent felonies or serious drug offenses.

Robertson has at least eight past convictions dating back to 1998 that include larceny, robbery, criminal possession of a weapon, kidnapping with a firearm and possession with intent to distribute narcotics.