New York ? A man already serving time in a state prison for the sniper-shooting death of a doctor was convicted Thursday on a federal charge of targeting and killing the man because he provided abortions.

The jury deliberated about four hours over two days before deciding James Kopp violated the federal Freedom of Access to Clinic Entrances Act in the 1998 slaying of Dr. Barnett Slepian.

Kopp, who represented himself during the two-week trial, tried to convince jurors during his closing arguments that he didn’t mean to kill Slepian when he fired from woods into the doctor’s Amherst home. Kopp said he intended only to wound him to prevent him from performing abortions the next day. He’s serving a 25-year-to-life state sentence.

Assistant U.S. Attorney Kathleen Mehltretter argued Kopp’s planning of the shooting and his choice of weapon – a Russian military assault rifle – proved his deadly intent.

Federal prosecutors will seek a prison term of life without parole, U.S. Attorney Terrance Flynn said. Sentencing is set for June 19.