DES MOINES, Iowa (CBS NEWS) -- Authorities apprehended a man Wednesday suspected in the early morning killings of two Des Moines area police officers who were shot to death while sitting in their patrol cars in what authorities described as separate ambush-style attacks.

Officers from the Dallas County Sheriff’s Office and Iowa State Patrol took 46-year-old Scott Michael Greene into custody, police said. Des Moines Sgt. Paul Parizek said Greene was suspected in the killings but hasn’t yet been charged. He was being treated at a Des Moines hospital.

His arrest came about eight hours after the killings of two officers. CBS Des Moines affiliate KCCI-TV reports the arrest happened shortly after 9 a.m.

Parizek told reporters that Greene was walking along a gravel road, flagged down a state Department of Natural Resources employee, presented his driver’s license and told the employee to call 911.

Police 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, 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,” Parizek said at an early morning news conference, during which he stopped briefly as he worked to control his emotions.

Parizek later identified the slain officers as Des Moines Police Sgt. Anthony “Tony” Beminio and Urbandale Police Officer Justin Martin. Beminio was married and had children, Parizek said. Martin was single.

Greene is white. Parizek said the officers killed also were white.

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 had identified Greene as a suspect in the killings, describing him as armed and dangerous.

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

“There is a clear and present danger to police officers,” Parizek said. He said officers were 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, 114 officers have died in the line of duty in 2016, according to the Officer Down Memorial Page. The number reflects a roughly 6 percent increase over last year.

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 heartbroken.”

Asked at a news conference about a video posted on YouTube that appears to show a man identified as Greene being removed from an Urbandale High School football game, Parizek said he was aware of the video but hadn’t seen it and couldn’t comment.

The video, dated Oct. 14, was posted by someone identifying himself as Scott Greene. It shows a confrontation with police who have removed him from a football game, apparently after he held up a Confederate flag near a group of African Americans. The person shooting the video, who is never seen, asks police to investigate an assault against him. The officers ask him to leave and tell him it’s inflammatory to display a Confederate flag at such a setting.

Urbandale Community School District spokeswoman Dena Soenke confirmed Greene was involved in an incident at a recent high school football game that drew police attention. She referred questions about the incident to the Urbandale Police Department.

Court records show Greene was jailed and charged with interference with official acts after resisting Urbandale police officers trying to pat him for a weapon on April 10, 2014. An Urbandale officer described him as hostile and combative. He entered a guilty plea and was fined.

Two days later Urbandale police were called to answer a complaint of harassment at the apartment complex where Greene lived. The complaint said he threatened to kill another man during a confrontation in the parking lot.

“I will kill you n-----. F---ing kill you,” Greene said to the victim, according to the complaint.

Greene was charged with harassment.

He pleaded guilty and received a suspended jail sentence and a year of probation. Court records show he completed a substance abuse and psychological evaluation.

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