In a rare conviction for on-duty use of force, a Hennepin County jury on Monday found a former Minneapolis police officer guilty of assault for kicking a man in the face.

Christopher Michael Reiter delivered a blow to the head of Mohamed Osman in May 2016, knocking him unconscious and inflicting brain bleeding and a traumatic brain injury, testimony at the trial showed.

Reiter, 36, had already lost his job with the Minneapolis Police Department and will now likely lose his peace officer’s license, as state law requires an automatic revocation for any felony conviction. He will be sentenced Dec. 12 for the third-degree assault conviction.

It’s unusual for a police officer to be prosecuted for on-duty misconduct, and even rarer for that officer to be convicted, a recent Star Tribune series showed.

Neither Reiter nor his attorney, Robert Fowler, would comment after the trial. Hennepin County Attorney Mike Freeman said he will ask a judge to sentence Reiter to prison.

“All Minneapolitans, including police officers, agree this conduct is not acceptable,” Freeman said in a statement. “You don’t kick a guy on his knees, in the face, especially when he wasn’t doing anything.”

In his closing argument, prosecutor Daniel Allard told the jury there was a conspiracy to protect Reiter that involved the defendant, another MPD officer and a victim of domestic assault. Each of them testified that Reiter believed Osman had a knife.

“It’s a coverup. Sad as it is,” Allard said. “But there’s no other conclusion here.”

On May 30, 2016, Reiter responded to a domestic abuse call at a south Minneapolis apartment building and found a woman badly beaten. When other officers arrived, they found the man who beat her, Osman, sitting in his SUV in front of the building. Officers surrounded him and ordered him out of the car.

Surveillance video shows that as Osman was getting on the ground, one officer, Josh Domek, kicked Osman twice. Reiter, who had just run from the building, then kicked Osman in the face. The MPD later fired Reiter, who had been on the force since 2012.

After the May 2016 incident, both Domek and Reiter wrote in their reports that they kicked Osman because they believed he was resisting. Neither wrote anything about a knife.

During testimony at the trial that began last week at the Hennepin County courthouse, a security guard and several officers there that night said Reiter never told them about a knife. The officer who investigated the case against Reiter, Sgt. Paul Paulos of the St. Paul Police Department, said no reports mentioned a weapon.

But at the trial, Minneapolis officer Luke Eckert testified he pulled a knife off Osman that night, but that he neglected to mention it in a report and then later did not tell the MPD’s internal affairs department during its investigation. MPD Sgt. John Sullivan, who investigated the internal affairs case against Reiter, said no one mentioned a knife to him, either.

The woman severely beaten that night testified that she told several people about Osman having a knife, including Reiter.

But Allard called several of those same people to the stand, each of whom said she never mentioned a knife. “A reason for why [the woman] would lie?” Allard said during his closing argument. “She doesn’t want to help out Mr. Osman. Who would? I’m not blaming her or anything, but she told an untruth.”

Reiter himself testified that the woman told him that Osman was armed and to be careful. But Allard argued that it defied common sense for him to not write or say anything about a knife after he kicked Osman. “He would have forgotten the most important reason for using force in his report,” Allard said.

Fowler, Reiter’s attorney, said his client’s report writing “is obviously not his strong point.”

“But that does not prove a giant conspiracy,” Fowler said during closing arguments. “We are not here to decide whether my client writes an insufficient report or he doesn’t elegantly choose his words.”

If Osman was armed, Fowler said it would have been reasonable for Reiter to kick him.

“It would be unreasonable if my client didn’t act given the threat level,” he said.

Minneapolis police have investigated eight complaints against Reiter. Before being fired, Reiter had kicked a gas station attendant while on duty in 2014. The attendant sued, and the case settled after the city of Minneapolis agreed to pay $105,000 after a federal lawsuit.