A boy riding his bicycle in Brockton last night was struck by a car and killed, police said.Brockton police Sgt. James Baroud said the boy, whose name was not released, was between the ages of 12 and 14. Baroud said he was struck while riding his bicycle on Main and Plain streets about 6:42 p.m.He said the driver of the vehicle that struck him stopped at the scene, and is being interviewed by police.He said the boy was pronounced dead at the scene.