DES MOINES, Iowa — Two Des Moines area police officers were shot to death while sitting in their patrol cars early Wednesday in what authorities described as separate ambush-style attacks, and police said they are searching for a known suspect.

Officers responded to a report of shots fired at 1:06 a.m. and found an Urbandale Police Department officer who had been shot. Authorities from several agencies saturated the area after that shooting, and about 20 minutes later discovered that a Des Moines officer who had responded to the initial killing had been shot in a patrol car at an intersection, Des Moines Sgt. Paul Parizek said. The shootings happened less than 2 miles apart and both took place along main streets that cut through residential areas.

“There’s somebody out there shooting police officers. We hope to find him before somebody else gets hurt,” said Parizek, who stopped briefly during a news conference as he worked to control his emotions.

The shootings follow a spate of police killings, including ambushes of officers in Dallas and Baton Rouge, Louisiana. Five officers were killed in Dallas on July 7 and three were killed later that month in Baton Rouge.

Des Moines and Urbandale Police later said they have identified 46-year-old Scott Michael Greene as a suspect in the killings, describing him as armed and dangerous and urging members of the public to not approach him if they see him, but to call 911.

Parizek said investigators determined Greene was a suspect through “a series of leads and investigative tips.”

Police described Greene, of Urbandale, as white, 5’ 11” and 180 lbs with brown hair and green eyes, last known to be driving a blue 2011 Ford F-150 with Iowa license plate 780 YFR.

“There is a clear and present danger to police officers,” Parizek said. He said officers are now conducting patrols in pairs for protection.

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.

Wednesday 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. With Wednesday’s deaths, 113 Iowa officers have died in the line of duty in 2016, according to preliminary data from the National Law Enforcement Officers Memorial Fund.

Fifty-one of those deaths were firearms-related, a spike from last year that the group has blamed on an uptick in ambush-style killings. That number has already surpassed the total number of officers fatally shot in each of the prior four years, but is on pace to fall short of the 73 fatally shot in 2011.

Urbandale is a suburb of about 40,000 people in the Des Moines metro area with about 50 officers. Des Moines, a city of about 210,000, has about 375 sworn officers.

Urbandale officers are equipped with body cameras, but they don’t run constantly and it’s 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, fueling 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.

Parizek said investigators have no idea what led to the killings, and he speculated that they may never be sure about the shooter’s motivations.

He said the officers’ deaths are a blow to all officers in the Des Moines area.

“They are our friends and co-workers,” he said. “Des Moines is not a big city. We all know each other. We’re heart broken.”

Iowa Gov. Terry Branstad called the killings, “an attack on the public safety of all Iowans.”

“We call on Iowans to support our law enforcement officials in bringing this suspect to justice. Our thoughts and prayers go out to the families of the police officers who were tragically killed in the line of duty as well as the officers who continue to put themselves in harm’s way.”