Federal authorities are looking for a convicted murderer from Georgia who is believed to have sexually assaulted a Georgia teen.

Zachary Byron Cobb, 54, was last seen at a Walmart in Richmond, Va. on Dec. 15, according to the U.S. Marshals Service. He is considered the “prime suspect” in the attempted abduction, robbery and sexual assault of the teenager. A parole violation warrant for Cobb, who served nearly 30 years in prison for a 1981 double murder, was issued on Dec. 18. Cobb is believed to be driving a silver 2006 Toyota Camry with Georgia tags BUV-5838.

Anyone with information about Cobb’s whereabouts is asked to call the U.S. Marshals Service at 1-877-926-8332.