One policeman was shot dead and three others shot and wounded in four US cities on Sunday, coinciding with an epidemic of racially-tinged gun violence involving law enforcement.
Police were shot in San Antonio, Texas, Sanibel, Florida, and in the Missouri cities of St. Louis and Gladstone, local police departments said.
There was no known connection between the shootings.
In San Antonio, authorities were hunting for a suspect who fatally shot 20-year service veteran Detective Benjamin Marconi twice in the head after being pulled over in traffic in front of police department headquarters.
Police, who are receiving support from federal and state law enforcement, offered a $10,000 reward for information leading to an arrest in the case, describing the unnamed suspect as a black male wearing a hoodie and baggie pants.