US police have arrested a man suspected of killing two police officers in Iowa.
Scott Michael Greene (46) was taken into custody without incident after two shootings in the Des Moines and Urbandale areas.
Greene is suspected of fatally shooting the officers as they sat in their patrol cars.
The arrest came about eight hours after the killings.
Des Moines Police Sgt Paul Parizek said Greene was arrested while on foot and was alone when he was taken into custody.
Officers initially responded to a report of shots fired at 1.06am local time, and found an Urbandale Police officer with gunshot wounds in a patrol car.
About 20 minutes later, a Des Moines officer who had responded to reports of the initial killing was also found shot in a patrol car at an intersection, less than two miles away.
The shootings follow a spate of police killings, including ambushes of officers in Dallas, Texas and Baton Rouge, Louisiana. Five officers were killed in Dallas on July 7 and three were killed later that month in Baton Rouge.
Sgt Parizek said investigators determined Greene was a suspect through "a series of leads and investigative tips".
Urbandale Sgt Chad Underwood said he believes this is the first time an officer in his department has been shot in the line of duty.
The incident marked the first time a Des Moines police officer has been shot and killed on duty since 1977, when two died in separate incidents months apart, according to the Iowa Department of Public Safety.
Urbandale officers are equipped with body cameras, but they do not run constantly and it is unclear whether there was video of the shootings.
The attacks on police this summer in Dallas and Baton Rouge came in the wake of several high-profile police shootings of black men, fuelling a national debate about police use of force, especially against minorities - a frequent topic in the nation's presidential race.
Republican nominee Donald Trump has argued that police need the freedom to use greater force, while Democrat Hillary Clinton has taken a more nuanced position of supporting officers while calling attention to what she and others have called examples of bias in policing.
Sgt Parizek said investigators have no idea what led to the Iowa killings, adding that the deaths were a blow to all officers in the area.
"They are our friends and co-workers," he said.
"Des Moines is not a big city. We all know each other. We're heartbroken."
Asked at a news conference about a video on social media which appeared to show a man identified as Greene being removed from a high school football game, Sgt Parizek said he was aware of the video but had not seen it and could not comment.
