US police have arrested a man suspected of killing two police officers in Iowa.
Scott Michael Greene, 46, was taken into custody without incident eight hours after the two shootings in the Des Moines and Urbandale areas.
Greene is suspected of fatally shooting the officers as they sat in their patrol cars. 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.
Des Moines Police Sergeant Paul Parizek said Greene was arrested while on foot and was alone when he was taken into custody. He said investigators determined Greene was a suspect through "a series of leads and investigative tips".
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.
The shootings follow a series of police killings including ambushes of officers in Dallas, Texas and Baton Rouge, Louisiana.
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.
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.
"They are our friends and co-workers," Parizek 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, Parizek said he was aware of the video but had not seen it and could not comment.