Police are searching for the person who shot and killed a man on a Charlestown street shortly after 10 p.m. Tuesday. Boston police responded to Monument Street around 10:18 after receiving 911 calls. After they arrived, they found the body of a man in the street near 92 Monument St. He was pronunced dead at the scene. Police said they know who the victim is, but are not releasing his name. No arrests have been made, police said.