DENVER (AP) — A man who shot and killed a Colorado deputy and wounded four others along with two civilians was an attorney and an Iraq war veteran who had posted videos online in recent months criticizing professors and law enforcement officials, authorities said Monday.

Shooter Matthew Riehl, 37, died Sunday during what officials called an ambush at his apartment building in Highlands Ranch, 16 miles (28 kilometers) south of Denver.

Authorities say Riehl fired more than 100 rounds in his apartment before he was killed by a SWAT team.

Douglas County Deputy Zackari Parrish was killed.

Authorities had been contacted with concerns about Riehl's mental health over a month before the violence Sunday, however Riehl was never held for mental evaluation.

Wyoming College of Law students had been warned about Riehl, a former student, because of the social media posts critical of professors at the school in Laramie, reported KTWO-AM in Casper, Wyoming.

A Nov. 6 email from Assistant College of Law Dean Lindsay Hoyt told students to notify campus police if they saw Riehl or his car near campus.

In addition, security on campus was increased for several days.

Campus officers called police in Lone Tree, Colorado, in mid-November to warn them about Riehl, suggesting his rants were indicative of mental illness, UW Police Chief Mike Samp told The Denver Post.

Samp said it's possible that Colorado authorities faced the same issue as Wyoming officials when an apparently mentally ill, dangerous person makes indirect threats.

"Wyoming statutes are pretty clear: If someone is not making an immediate threat, they cannot be held for a mental evaluation. They are very tough cases," Samp said.

Riehl had posted videos criticizing Colorado law enforcement officers in profane, highly personal terms.

Early Sunday, authorities responded to a complaint of a verbal disturbance involving two men at an apartment. A caller said Riehl was acting bizarre and might be having a mental breakdown, but responding deputies found no evidence of a crime and left.

When deputies were called back to the scene, a man who had left gave them a key and granted permission to enter the apartment.

All of the wounded victims except Deputy Jeff Pelle, 32, have been treated at hospitals and released. The son of Boulder County Sheriff Joe Pelle was in fair condition.

A candlelight vigil for Parrish was set Monday evening at Mission Hills Community Church in Littleton, Colorado — the church he attended with his wife and two young daughters.

"I've heard from so many different people that he just loved his community and being a police officer," Mission Hills Pastor Craig Smith told KDVR-TV.

"Zack didn't see law enforcement as a job. He saw it as a calling, as a way to serve his community and a blessing."