An off-duty federal agent went to the aid of a 51-year-old motorist Wednesday morning as he was being attacked by two Manteca men.The victim was driving out of the Kmart parking lot on Northgate Drive west of North Main Street when the incident happened.The federal agent detained the suspects at gunpoint until Manteca officers arrived. Manteca Police Sgt. Jodie Estarziau said the motorist was hesitating as he drove out of the parking lot to let the two men walk by the front of his car on the sidewalk. One of the men allegedly threw a hamburger at the windshield of his vehicle as he waited.