A manhunt is under way in Texas for a suspect wanted in the fatal shooting of a veteran police detective in what authorities say was one of several attacks targeting law enforcement in multiple states.
The San Antonio detective as well as officers in Missouri and Florida were conducting routine tasks on Sunday when they become the targets of violence.
The detective was writing a traffic ticket when he was shot to death in his squad car outside police headquarters.
In St Louis, Missouri, a police sergeant was shot twice in the face on Sunday evening while he sat in traffic in a marked police vehicle. The man has since been released from hospital.
Police officers were also shot and injured during traffic stops in Sanibel, Florida, and Gladstone, Missouri, on Sunday night, but authorities have not suggested these were targeted attacks.
The shootings come less than five months after a black military veteran Micah Johnson killed five white officers at a protest in Dallas - the deadliest day for American law enforcement since September 11, 2001.
Race was a factor in the Dallas attack but police have not said if race played a part in any of the attacks on Sunday.
In San Antonio, police say the suspect is black and the officer was white. In St Louis, the suspect was black. Police have not released the race of the officer he shot.
San Antonio police chief William McManus identified the officer killed on Sunday as Benjamin Marconi, 50, a 20-year veteran of the force.
Mr McManus added: "I think the uniform was the target and the first person that happened along was the first person that (the suspect) targeted."
Police said the search for a male suspect was still under way on Monday and that no arrest has been made.
Surveillance video shows the suspect at San Antonio police headquarters about four hours before Mr Marconi was shot.
The suspect asked a desk clerk a question but left before receiving an answer, said Mr McManus, who declined to say what the man asked.
St Louis police chief Sam Dotson declined to name the 46-year-old officer on his force who was shot in the face, but said he is a married father-of-three who has been with the department for about 20 years.
The suspect was wanted for questioning in recent violent crimes that included several robberies, a carjacking and perhaps a killing, Mr Dotson said.
"We believe he knew he was good for those crimes and that we were looking for him," Mr Dotson said. "That's why he aggressively attacked a police officer."
Police said the suspect was later killed in a shootout with police. The suspect's name was not released but Mr Dotson said he was black and born in 1997.
An officer with the Gladstone police department near Kansas City was shot while the suspect was shot and killed. The officer is out of surgery and expected to recover.
A Sanibel officer was shot in the shoulder during a traffic stop and was treated for his injuries and released.