US: Suspect held for killing 2 officers 'ambush-style'

Greene shot dead two police officers at approximately 1 a.m. (0600GMT) in "ambush-style attacks", the Urbandale Police said in a statement.

Both officers were sitting in separate cars when attacked, police officials told the media at a later conference.

The motive for the attack remains unclear. “We’re not anywhere close to that,” Parizek said. “We may never know what motivated this act.”

He added that there does not appear to have been any interaction between the officers and Greene before the shootings.

In a statement, President Barack Obama said that the slain officers, whom he identified as Anthony Beminio and Justin Martin, "represented our best, most decent instincts as human beings – to serve our neighbors, to put ourselves in harm’s way for someone else.

"As we once again mourn American police officers lost in the line of duty, we must also renew the call to match that same sense of service, that same devotion within our own lives and our own communities," he said.

A 10-second YouTube video, titled "Civil Rights Violation at Urbandale High School 10/14/16" that was published Oct. 21 under an account named Scott Greene, features a single snapshot showing a man matching police descriptions of Greene holding American flags at what appears to be a high school football stadium.

A separate 11-minute video of the same incident published Oct. 16, shows Greene interacting with police officers, who tell him repeatedly, "Sir, I'm asking you to leave this property," as the stadium lights shine in the background.

"Have I committed a crime?" Greene asked the officers. "I think I have been assaulted by you. You grabbed me," he said, while the officers remain calm and non-aggressive.