Copper Canyon Apartment Homes shooting

Deputies confirmed that Zackari Parrish was shot multiple times and died at the scene from his injuries. He had been working for the department for seven months having previously worked for the nearby Castle Rock Police Department. He was also married and had two young children. The funeral took place on January 5, 2018. The procession started at Plum Creek and finished at Cherry Hills Community Church and was accompanied by a motorcade.

The Copper Canyon Apartment Homes Shooting was a shooting on December 31, 2017, in Highlands Ranch, Colorado. One police deputy, Zackari Parrish, was fatally shot, and four others were wounded. Two civilians were also shot by the suspect, who was later killed in an exchange of gun fire with a SWAT tactical team. The suspect reportedly used a rifle and a shotgun. Law enforcement had responded first to a noise complaint, then to a domestic-disturbance call to the apartment. During the second visit, the suspect barricaded himself in his bedroom and shot the deputies in an "ambush" style when they entered. The suspect was later shot dead by a police tactical team that subsequently re-entered the apartment. It was later determined that the suspect, former attorney Matthew Riehl, was a veteran with a history of psychotic episodes and he had recently stopped taking his medication.

After receiving a speeding ticket on November 10, 2017, Riehl filmed seven YouTube videos where he "ranted" about the incident and likened the officer who issued the ticket to a Nazi. He also sent at least 18 emails to the LTPD and the issuing officer for the ticket to be dismissed. Riehl became the subject of an investigation which concluded that Riehl had not threatened anyone and therefore his actions were not criminal. On December 12, a 'Hazard Hit' was placed on his address, stating that there needed to be a "Minimum 2 Car Response" from police when attending. The LTPD also concluded that he had post-traumatic stress disorder (PTSD).

On December 31, 2017, at 2:58 am, Riehl called 9-1-1 to report a verbal disturbance. Deputies Zackari Parrish and Taylor Davis, and Corporal Aaron Coleman arrived at the apartment at Copper Canyon Apartments where they spoke with Riehl and the owner, Matthew Thompson, who was allowing Riehl to stay there. According to Coleman, he and Parrish walked up the stairs to the apartment where Riehl answered the door and came to speak to Coleman, while Parrish entered the apartment to talk with Thompson. Coleman described Riehl as acting "erratic[ly]". Riehl explained that he wanted to have called an ambulance because Thompson was acting strangely and believed he was having a PTSD flashback, and also because Riehl had pointed a laser in his face after he had approached him. After Riehl then attempted to return to the apartment, Coleman stopped him by placing a hand on his chest before Riehl began shouting, which he stopped after Coleman told him to be quiet.

After being honourably discharged in 2012, Riehl developed mental health issues; in March 2014, his brother phoned the police for a welfare check on Matthew and he later went to hospital for treatment. In April, he was in a United States Department of Veterans Affairs (VA) mental health ward having experienced a psychotic episode before he escaped and was later found and brought back. On June 9, 2016, Lone Tree Police Department (LTPD) responded to an altercation between Riehl and his father. On June 8, 2017, LTPD again met with Riehl to conduct a welfare check; they talked for 14 minutes and claimed to have seen rifles in his basement, but had no reason to believe he was a danger to himself or others.

Matthew Riehl (September 9, 1980 – December 31, 2017) attended CU Denver, graduating magna cum laude in 2004, according to his mother. He had joined as an army reserve in 2003 before serving in the Iraq War as a combat medic whilst attending law school at the University of Wyoming, which he graduated from after returning from Iraq. He then went to work for a law firm in Rawlins, Wyoming for three years before leaving to set up his own practice. He joined the United States National Guard in 2006 reaching the rank of Specialist and serving from 2009 to 2010, again as a medic, in Kuwait and Iraq in the 300th Field Artillery Regiment where he didn't face combat. Riehl was involved in escorting convoys of troops 130 miles (210 km) through the desert at night.