DENVER — A Denver Police Department officer has resigned, 17 months after body camera footage showed him assaulting a man already in handcuffs.

Cpl. Michael Oestmann’s resignation letter is dated July 24.

Oestmann’s use of force investigation began in April 2018 after his body camera caught him slamming a 30-year-old assault suspect.

Kevin Watson was handcuffed to a chair in the basement of Jackson’s Sports Bar for allegedly punching another bar patron.

Oestmann was working off-duty at the bar when video shows an intoxicated Watson spitting and repeatedly swearing at the officer.

“You scared, you in uniform, you scared?” Watson can be heard saying while challenging Oestmann to uncuff him so the two can fight.

Oestmann mostly ignores Watson until the handcuffed suspect spits in his face.

At that moment, Oestmann slams Watson into a locker and yells, “You will not spit on me again, do you understand?”

Watson is briefly knocked unconscious and Oestmann can be heard on the body cam saying, “What was that about being a (expletive)? Who’s unconscious now?”

Oestmann was charged with third-degree assault.  In March, the Denver District Attorney’s Office announced it had struck a diversion deal with Oestmann, allowing him to have his record wiped clean if he completed anger management classes and probation.

The Department of Public Safety provided a copy of the Internal Affairs report but redacted the section devoted to “Analysis and Conclusions.”

However, sources said police Chief Paul Pazen was prepared to terminate Oestmann, who opted to resign first.