The Aurora Police Department SWAT officer who shot and killed unarmed Kilyn Lewis in May during an attempted SWAT arrest has officially been cleared from both disciplinary actions and criminal charges.

The department completed its administrative investigation regarding the incident and determined that Officer Michael Dieck — a 13-year-veteran of the department and eight-year Aurora SWAT team member — did not violate agency policy when he shot 37-year-old Lewis in the stomach on May 23, according to a Friday news release from the department.

The review included the Aurora Police Department’s Force Investigations Unit, the Force Review Board — which includes the city’s chief of police — and the Independent Consent Decree Monitor, according to the release.

“The review concluded Officer Dieck was not in violation of agency policy or misconduct,” the department said.

Dieck was placed on restricted duty by the department on Aug. 3 and was assigned to the Electronic Support Section, where he currently remains following the decision, a spokesperson with the department told The Denver Gazette.

The decision comes a little over a month after the investigation held by the 18th Judicial District’s Critical Incident Response Team (CIRT) also deemed Dieck justified in his use of force, with the district attorney deciding there was no basis to file criminal charges against the man.

“I find that there is no criminal liability on the part of Officer Michael Dieck stemming from this OIS (officer-involved shooting). Criminal charges, therefore, are not appropriate or warranted related to the officer’s use of deadly force,” District Attorney John Kellner said in the Oct. 11 letter.

The case was also presented to the Arapahoe County Grand Jury, which found insufficient evidence to charge Dieck.

The incident

The shooting — which brought about a significant amount of protest at Aurora City Council meetings, with Lewis’ family speaking at nearly every meeting since the death — started as an attempted arrest by the both Denver and Aurora SWAT teams around noon on May 23.

The teams attempted to arrest Lewis on a warrant for attempt to commit first-degree murder after the man was connected to an attempted homicide in Denver on May 5 in the area of 48th Avenue and Colorado Boulevard around 11:30 a.m.

Officers from both departments confronted him outside an apartment complex on South Ironton Street in Aurora. Lewis was working on a red vehicle that appeared in security camera footage connected to the May 5 shooting.

Four officers, including Dieck, exited vehicles with weapons drawn to arrest Lewis. They commanded the man to drop to the ground, but Lewis walked toward the driver’s side door and pulled a cellphone and tube with a fruit snack in it from his back right pocket.

Dieck ultimately fired a shot into Lewis’ abdomen, leading to his eventual death at a nearby hospital.

While cocaine was found in Lewis’ pants after the shooting, no gun was found at the scene, according to the district attorney’s letter.

In follow-up interviews conducted by CIRT, Dieck claimed that he believed Lewis pulled a firearm from his pocket, causing him to fire at the suspect.

When Dieck saw Lewis rummaging in his pocket, he believed he was pulling a gun because, based on his experience, “relatively few people who illegally carry guns utilize a holster, but instead carry their guns in the waistband or a pocket,” the letter said. He also claimed it wasn’t common for someone to start reaching into their pants when approached by officers randomly, instead usually freezing from shock.

The other officers involved supported Dieck’s concerns about Lewis pulling a gun, calling Lewis’ behavior in the face of arrest “unusual.”

Prior to being cleared in the killing of Lewis, Dieck was involved in two other shootings and one arrest that led to the conviction of another Aurora police officer.

On July 23, 2021, Dieck was involved in the arrest of Kyle Vinson, which led to a criminal trial against a former officer, John Haubert, according to the Aurora police.

Haubert hit Vinson 12 times with the butt of his gun during the arrest, drawing blood from wounds that required stiches. The incident led to charges of assault and misconduct. Haubert was found not guilty following a 2024 trial.

Dieck was not charged in any of the incidents.

Aurora’s consent decree monitor — which was initially set up following the handling of the death of Elijah McClain in an effort to improve how officers use force and interact with people of color — questioned the use of force in its report on the incident in October.

“I think there are issues that have to be answered,” said Jeff Schlanger with IntegrAssure, Aurora’s independent consent decree monitor.

“There were some questions that were raised relative to the facts and circumstances surrounding the involvement of APD because this was a Denver arrest warrant that was being executed,” Schlanger continued. “And there were questions with respect to the tactics that were employed, including whether or not there were less lethal options available during the encounter.”

The report also raised the concern of how the department selects and retains its SWAT officers, especially with Dieck’s past of two previous shootings.

According to the department’s spokesperson, Dieck will not be returning to the SWAT team, where he spent the last eight years, despite being deemed justified in his use of force.

Prior to the internal investigation’s conclusion, new Aurora Police Chief Todd Chamberlain began reviewing all agency operations, which includes an assessment of SWAT functions, according to the release.

Chamberlain’s hire was approved by the city council on Aug. 26.

“As with all department functions, we will ensure that the operations not only align with industry best practices, but also with our mission to make the city of Aurora a safe community to live, work and raise a family,” Chamberlain said in the release. “The review is being done in the spirit of the principles of the consent decree including transparency, continuous improvement and accountability to our residents.”

In a response to the investigation results Friday, Schlanger raised the fundamental question: Are the current policies and training frameworks guiding SWAT operations in Aurora aligned with the highest standards of national best practices?

Schlanger noted that the initial report by the consent decree monitor was to initiate questions regarding Aurora SWAT’s threat assessment, tactical decision-making and de-escalation strategies under high-risk circumstances — not just in the Lewis shooting, but overall.

The review that Chamberlain began when he entered the role is a step forward, according to the consent decree monitor.

“It is clear that Chief Chamberlain’s commitment to a comprehensive review of SWAT recognizes the need for analysis and will focus on precisely these areas,” Schlanger told The Denver Gazette. “This review is expected to scrutinize and, if necessary, recalibrate the policies, practices and training that shape SWAT operations to ensure they align with evolving national standards and best practices.”

Overall, Schlanger added that the commitment to transparency and improvement is promising, especially for a department that experienced drastic scrutiny with its actions during the McClain death, prior to the establishment of the independent monitor.

“The decisions made by the leaders of Aurora are a grave injustice,” Lewis’ family said in a public statement on Oct. 11, following the decision from the district attorney’s office. “Just like those before us who have been faced with these tragedies, our fight will continue without disruption. This decision is not only a failure of justice but a message that the life of an unarmed Black man like Kilyn means nothing to the very system that is supposed to protect us.”

The Denver Gazette’s news partner, 9News, contributed to this report