Two Iowa police officers were shot and killed early today while sitting in their patrol cars in what authorities called separate and unprovoked ambushes, and a 46-year-old suspect was captured hours later, police said.
The man, Scott Michael Greene, was taken into custody in the killings in the Iowa capital Des Moines and its affluent suburb Urbandale, a police spokeswoman said. Police said it was unclear what provoked the attacks.
The shootings represented the latest attacks on police in the United States during a time of intense public debate over race and the criminal justice system in America.
Police said they found the first slain officer's body at about 1:06am (0606 GMT) in Urbandale, and the second about 20 minutes later about two miles (3 km) away in Des Moines. Police declined to release the names of the officers awaiting notification of their families.
A police cruiser at the site of the Des Moines shooting could be seen riddled with three bullet holes.
Scott Michael Greene has been apprehended."These officers were ambushed," Des Moines police spokesman Paul Parizek told a news conference prior to Greene's arrest.
It appeared the suspect, who is white, had a recent run-in with police.
A 10-minute video posted on YouTube last month by a user calling himself Scott Greene showed an interaction with officers following an incident at a high school stadium in which he described holding up a Confederate battle flag during the playing of the US national anthem at a football game.
Reuters was unable to immediately confirm whether the video was made by the suspect, whose face does not appear in it. It records a male voice arguing with police over the incident.
The man is heard complaining to police that "African-American people" took the flag from him in the stands, "assaulted" him, and saying he wanted to press charges.
Police officers shown in the video said he was removed from the stadium because he caused a disturbance in the stands.
The Confederate flag is a racially charged symbol for its association with the pro-slavery South in the US Civil War.
"You have to understand, in the current social climate that we're in, when you fly the Confederate flag standing in front of several African-American people, that's going to cause a disturbance, OK, whether you intended to or not," a female officer is heard telling the man.
US Attorney General Loretta Lynch urged Americans to avoid jumping to conclusions about the shooter's motive.
"This is a time of particular tension and mistrust between law enforcement and many communities," Lynch said at an event for veterans at the Justice Department in Washington. "There is no message in murder. Violence creates nothing. It only destroys."
Before the shootings in Iowa, 50 police officers had died by gunfire, two accidentally, in the line of duty in the United States this year, according to the Officer Down Memorial Page website.
A black Afghan war veteran who said he wanted to "kill white people" fatally shot five police officers during a Dallas protest decrying police shootings of black men in July.
A black Iraq war veteran fatally shot three officers and wounded three others in Baton Rouge, Louisiana, in an ambush later in July.
Both of those attacks on police followed fatal shootings by officers of black men in Minnesota and Louisiana.
Philadelphia police officers have been targeted by a gunman twice this year.
The Iowa killings came two years after two New York police officers were shot dead sitting in their patrol car in Brooklyn by a man who said he wanted to avenge the deaths of unarmed black men killed by police.
Today's shootings came seven months after two Des Moines officers were killed when their vehicle was hit by a drunken driver. Another Des Moines police officer died in a motorcycle accident in August.
Democratic US presidential candidate Hillary Clinton's campaign canceled an event in Iowa today with former President Bill Clinton and vice presidential candidate Tim Kaine after the shootings.
Republican candidate Donald Trump said on Twitter that he was praying for the slain Iowa officers' families, adding, "An attack on those who keep us safe is an attack on us all."