Riehl was also shot and killed on the scene.
The suspected gunman was also shot and the sheriff's office says he's believed to be dead.
Samp said it's possible that Colorado authorities faced the same issue as Wyoming officials when an apparently mentally ill, risky person makes indirect threats. He says the weapons in the photos belonged to the suspect.
Riehl's Facebook page was filled with images associated with the alt-right. The Libertarian Party of Colorado said it had no contact with him.
"We do know that it was a rifle-and other than that I can't tell you", Spurlock said. "He knew we were coming", said Spurlock.
Riehl shared the apartment with a male roommate who was uninjured and is cooperating with authorities. He was not injured.
The gunman, identified as Matthew Riehl, was later shot dead by the officers.
"It's OK, momma, it's OK", whispered their 4-year-old daughter in her ear. "This is Colorado. Everybody has a gun", Mr Spurlock said.
The shooter, whose name was not released, was killed by law enforcement officers about an hour after gunfire erupted at the Copper Canyon Apartments. A graduate of Dallas Baptist University, Parrish studied communications in college and initially worked in banking.
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Parrish, who suffered multiple gunshot wounds, leaves behind a wife and two young children.
Pictured the Highlands Ranch apartment complex, Denver, where Deputy Zackari Parrish was fatally taken down.Deputy Zackari Parrish dream job was to work for law enforcement. Four other officers and two civilians also were injured. The civilians who were shot, all survived.
Two civilians were also hurt, although neither received major injuries.
O'Donnell is an officer with Castle Rock Police.
"He is in good spirits considering the gravity and severity of what occurred earlier this morning", they said in the statement.
Several local police agencies and the Colorado State Patrol were put on alert. Police said all of the deputies were wearing bulletproof vests, but that they were struck by bullets in unprotected parts of their bodies.
The shooting prompted a large police response.
"It's never easy", Spurlock said.
The man continued to shoot at officers for "some time", until he was engaged by officers and killed.
Authorities were asking everyone in the area to take shelter and avoid windows and exterior walls. That order has since been lifted.
Police and family mourned the slain officer at a vigil Monday night, KUSA reported.
This story is ongoing and will continue to be updated as new information becomes available.