The man who killed a deputy and injured four officers and two civilians on New Year's Eve in Highlands Ranch had a history with law enforcement in Colorado and Wyoming, was estranged from his family and reportedly was living with mental health issues.

Matthew Riehl, 37, was killed in a Dec. 31 shootout with authorities. Douglas County Sheriff Tony Spurlock said Riehl used a rifle to fire at least 100 rounds at officers during a two-hour standoff before a regional SWAT team killed the suspect.

Deputy Zackari Parrish, 29, a husband and father of two, died in the early morning incident.

It remains unclear why Riehl began shooting at officers, but details of his past continued to emerge in the days after the New Year's Eve incident.

Riehl was well-known to law enforcement in both Wyoming and Colorado.

The University of Wyoming police department began investigating Riehl after he made a series of “alarming” social media posts concerning the university's law school and its professors, university spokesman Chad Baldwin said. The school increased security, warned students, staff and faculty and contacted the police department in Lone Tree — where Riehl lived after leaving Wyoming — about Riehl's behavior.

Lone Tree incidents

The Lone Tree Police Department released a timeline on Jan. 2 outlining the agency's interactions with him.

Lone Tree police first encountered Riehl when responding to a family disturbance in June 2016, when Riehl was in an altercation with his father. The family did not press charges.

In another incident, Riehl was issued a citation for careless driving for a traffic accident he was involved in on Feb. 18, 2017.

On June 8 of last year, police conducted a welfare check on Riehl at the request of his mother, who had concerns about his mental health. Officers spoke with Riehl for nearly 15 minutes through a closed door because he would not let them in. Riehl stated he was not a danger to himself or others. Police provided mental health service information to Riehl and his family, but the family declined services, the department said. 

Police conducted another welfare check in August after Riehl reported his mother and brother had formed a suicide pact. Police determined that information was not true.

On Nov. 10, a Lone Tree police officer issued Riehl a speeding ticket, which resulted in a court summons. Later that month, Riehl began sharing social media posts and YouTube videos about the traffic stop, alleging the officer lied to him and conducted an “illegal” stop. The Lone Tree Police Department said his behavior “escalated to include harassing emails directly to LTPD police officers.” Because Riehl had moved to Highlands Ranch by then, police contacted the Douglas County Sheriff's Office to investigate, according to the department's timeline.

On Nov. 14, a detective with the University of Wyoming Police Department contacted Lone Tree police regarding their investigation into Riehl's comments toward the university.

“Given that this remains an ongoing investigation, additional details may not be available. However, throughout this time period, LTDP has fully collaborated and cooperated with DCSO, the University of Wyoming Police Department and the suspect's family on each incident involving Riehl,” the timeline said.

Guns, livestreamed tirades

A University of Wyoming Police Department report obtained by the TV station/news website Denver 7 and reported on by several media outlets shows family and friends told police Riehl suffered from post-traumatic stress disorder, was bipolar and was off his medications. He was also estranged from family in recent weeks and had mental breakdowns, the report said, although police did not find evidence Riehl had threatened violence toward others.

Colorado Community Media requested the report but it was not immediately made available. On Jan. 3, a spokesman for the university police department said the report has been placed under review — meaning some of the information in it could be redacted — while Colorado authorities continue to investigate the Dec. 31 shooting.

Multiple media outlets, including the Associated Press, have reported on the contents of a Periscope video shot by Riehl after news broke that he had livestreamed the New Year's Eve shooting. The video, showed in part by local TV stations, appears to show Riehl making one of the two 911 calls that brought officers to his residence that morning.

During the livestream, Riehl tells dispatch he'd been drinking, owned guns and was the victim of domestic assault during an argument with his roommate. He also claimed he'd purchased more than 1,000 rounds of ammunition. Media later reported on police records showing Riehl allegedly purchased 11 guns at a Laramie, Wyoming, gun shop several years ago.

Recent firearm training

In recent months, Riehl sought firearm training with Kenaz Tactical Group, a shooting school based in Colorado Springs. In a news release from the business, owner Robert Butler said Riehl attended defensive firearms courses conducted by the company over the summer.

“Mr. Riehl's demeanor during the training sessions was not alarming, he interacted well with other students and seemed proud of his military career. Mr. Riehl provided his own firearms during the training sessions,” the release said.

In speaking with Colorado Community Media, Butler said the company instructs a range of students, from civilians to first responders to military and other armed professionals. The defensive firearms course Riehl attended covers the “legal, moral and ethical use of” firearms specifically in self-defense, Butler said.

“We do talk about natural body responses to a threat,” he said. “We always encourage that fight is your last response.”

The company's release said it is prepared to fully cooperate with authorities leading the investigation.

A former lawyer, veteran

Sharon Wilkinson, executive director of the Wyoming State Bar, confirmed to Colorado Community Media that Riehl was a licensed attorney in the state from 2011 to October 2016, when he voluntarily withdrew his membership. Riehl did not give a specific reason for leaving the bar, she said.

“It's not uncommon for attorneys to withdraw their membership in the month of October,” Wilkinson said.

Membership fees are payable on Oct. 1 and due by the end of November. Attorneys who have moved out of the jurisdiction frequently withdraw if they know they will not practice in the area again, she said. The organization was notified Riehl changed his address to Lone Tree in July 2015.

Before withdrawing, Riehl practiced law with MacPherson, Kelly & Thompson LLC., a firm in Rawlins, Wyoming. A statement from the firm said Riehl was employed there from 2011-14 as an associate attorney.

“MacPherson, Kelly & Thompson, LLC has had no contact with Mr. Riehl, either socially or professionally, since he left the firm. MacPherson, Kelly & Thompson, LLC expresses its heartfelt condolences and deepest sympathies to the victims and their families,” the statement read.

Riehl also opened his own private practice in 2014, Wilkinson said. The organization did not receive any complaints about Riehl while he was a practicing attorney.

“That's about all we know about him,” Wilkinson said.

Deidre Forster, a spokeswoman for the Wyoming National Guard, also confirmed Riehl entered the Army Reserve in 2003 and the Wyoming National Guard in 2006. He was deployed to Iraq for a year in 2009 and was honorably discharged in 2012.

Ongoing investigation

A spokeswoman for the Douglas County Sheriff's Office said several officers were placed on paid leave following the shooting that killed Riehl, although further inquiries were not immediately returned.

Colorado Community Media has not confirmed what the sheriff's office did with the information provided by the Lone Tree Police Department or if deputies were told to take extra precautions when responding to Riehl's home on Dec. 31.

Updates regareding the shooting investigation will be shared on the sheriff's office's social media platforms, the agency has said.