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The man who launched a deadly attack on four police officers inside a Colorado apartment was a former Army Reservist who was deployed in Iraq for a year, a spokesperson for the military said Monday.

Authorities identified the gunman — who was killed in Sunday’s shooting — as 37-year-old Matthew Riehl.

Riehl barricaded himself in a bedroom in his apartment in a Denver suburb before suddenly opening fire with a rifle and shooting four deputies who were in the apartment responding to a complaint.

One of the deputies died. Five law enforcement officers and two civilians were injured in shooting exchanges before the suspect was killed by a police tactical team, authorities said.

Riehl served with the Wyoming National Guard from 2006-2012, according to Deidre Forster with the Wyoming National Guard’s office of public affairs.

Forster told CNN that Riehl enlisted in the Army Reserve in 2003. He spent time in Iraq in 2009 as part of a security mission during a one-year deployment with the 300th Field Artillery Regiment, according to Forster. He was honorably discharged in 2012 as an E-4 (Specialist), Forster said.

Douglas County Sheriff Tony Spurlock told reporters on Sunday that Riehl had previous contacts with law enforcement “throughout the metro area,” but had no criminal history.

Spurlock said the four injured officers were in stable condition.

“A tragic day that we will be feeling for a long time”

Spurlock identified the slain deputy as Zackari Parrish, a 29-year-old father of two. “This is a tragic day that we will be feeling for a long time,” said the sheriff. “Zack was a good kid, smiley kid. He was eager to work, eager to serve.”

A law enforcement motorcade accompanied the fallen officer from a hospital in nearby Littleton to the coroner’s office on Sunday.

President Trump tweeted his “deepest condolences to the victims of the terrible shooting in Douglas County … and their families.”

‘Well over 100 rounds fired’

The incident began about 5:17 a.m. when the first deputy arrived at the Copper Canyon Apartments in Highlands Ranch, about 20 miles south of Denver.

It was the second time deputies had gone to the apartment Sunday. There was a noise complaint call at around 3 a.m., but when deputies got there, there was no noise. After they spoke with a roommate in the apartment, they left, the sheriff’s office said.

“One male said the suspect was acting bizarre and might be having a mental breakdown,” a police news release said.

The second call was dispatched as a domestic disturbance, and by 5:35 a.m. the four deputies had arrived at the scene.

The sheriff’s office said the roommate returned to the scene, gave deputies a key and said they could enter the residence. The roommate then left, police said.

Not long after the deputies found the suspect barricaded in his room, Riehl opened fire, Spurlock said.

“There were well over 100 rounds fired,” Spurlock said, adding that the deputies “all went down within almost seconds of each other, so it was more of an ambush type of attack on our officers.”

The wounded deputies crawled to safety as other law enforcement agencies responded to the shots fired call.

The suspect was killed about 90 minutes later during a shootout when a tactical team went into the apartment, the sheriff’s office said.