A man fleeing a car crash near Boston stole a cop’s gun and then shot him and a civilian dead Sunday, officials said.

Weymouth, Mass., Officer Michael Chesna, 42, was chasing Emanuel Lopes, 20, after Lopes was involved in a car wreck around 7:30 a.m., when Lopes allegedly bashed Chesna with a stone, sending him tumbling to the ground.

Lopes then took Chesna’s gun and blasted him several times in the head and chest before resuming his flight, authorities said.

As other officers gave chase, Lopes allegedly squeezed off three more rounds, missing his pursuers but fatally striking an unidentified elderly woman sitting in her house.

Chesna, an Army veteran and father of two, later died at South Shore Hospital, masslive.com reported.

Lopes was caught, and hospitalized at South Shore with a leg wound. He will be arraigned on two counts of homicide Monday.