Philadelphia ? A man fatally shot his ex-wife inside his car at a strip mall, then drove with the body to another shopping center parking lot where he shot and killed one of her friends before killing himself, police said.

An off-duty highway police officer saw the shooting of Alla Elkin, 23, shortly after 10 a.m. Friday in northeast Philadelphia, authorities said. The officer flagged down an on-duty motorcycle patrol officer, and the two followed 45-year-old Alexander Elkin in his red Mustang about a mile to another strip mall, where Elkin shot Irina Sulimova, 35, police said.

After an exchange of gunfire with the on-duty officer, Elkin got back into his car and shot himself in the head with an automatic pistol, police Inspector Carl Holmes said.

Cpl. James Pauley said that investigators had not determined a motive for the shootings.