A witness to George Floyd's murder under the knee of ex-Minneapolis police officer Derek Chauvin three years ago is suing the city, alleging he was assaulted and endured emotional distress.

In the lawsuit filed Tuesday in Hennepin County District Court, Donald Williams accuses Chauvin of threatening him and other bystanders with Mace and ex-MPD officer Tou Thao of placing his hand on Williams' chest. As a result of the since-convicted officers' actions, Williams said he feared for his safety and endured pain, suffering, humiliation, embarrassment and medical expenses.

Williams' attorney Jeff Storms, who represented Floyd's family and other families in high-profile police killing cases such as the shooting of Daunte Wright at the hands of former Brooklyn Center officer Kim Potter, did not respond to requests for comment.

Minneapolis City Attorney Kristyn Anderson declined to comment.

Williams, 35, was outside Cup Foods corner store around 8 p.m. May 25, 2020, when he saw Chauvin kneeling on Floyd's neck for nine minutes and 29 seconds as Floyd begged for his life. In the video of Floyd's killing captured by another bystander, Darnella Frazier, Williams was one of the most vocal bystanders urging Chauvin to get off Floyd's neck and for Thao to intervene.

"Chauvin looked directly at [Williams], grabbed his canister of Mace from his duty belt, and began shaking it at [Williams] and other bystanders," the lawsuit says. "[Williams] understand this gesture by Chauvin to be a threat to deploy Mace against [Williams] and other bystanders."

The lawsuit says that Thao taunted Floyd and bystanders who were expressing concern for Floyd's physical condition. Because Williams was vocal in his concern for Floyd, he alleged that Thao stepped toward him and placed his hand on Williams' chest.

He constitutes the actions of Chauvin and Thao as assault. Because of their "extreme and outrageous" conduct while acting as employees of the city, he filed two additional counts of emotional distress, one under intentional and the other as negligent.

For each of the three counts, he seeks at least $50,000 in damages.

Williams, a mixed-martial arts fighter, was a key witness in Chauvin's murder trial, explaining how Chauvin executed a "blood choke" on Floyd, a move restricting his circulation. "I called the police on the police," he testified. Asked why, he said, "Because I believe I witnessed a murder."

Chauvin is serving a 20-year prison sentence for Floyd's murder and for violating his civil rights. Thao, also serving a federal prison sentence for violating Floyd's civil rights, was found guilty of aiding and abetting Floyd's killing earlier this month and he will be sentenced in August.

The other officers involved — J. Alexander Kueng and Thomas Lane — are serving concurrent sentences ranging from 2 ½ to 3 ½ years for violating Floyd's civil rights and aiding and abetting manslaughter.

Williams stands accused of assault in a number of recent cases. Last week, he was charged in Olmsted County with three counts of misdemeanor assault and one count of disorderly conduct brawling/fighting. He was arrested by Rochester police May 7. No further detailed information is included in public court records and the city didn't immediately respond to a request for comment.

In a pending case in Anoka County from January he is charged with violating a domestic abuse no contact order. And in February, he was accused of arguing with an Eden Prairie gas station manager who told him to leave after he started yelling at staff. Charges of disorderly conduct accuse Williams of throwing mints that struck the manager in the face.

In September, Williams was charged in Ramsey County District Court with choking and striking his girlfriend in the face outside the Minnesota State Fair and threatening to kill responding officers.

He told police that he has post-traumatic stress disorder (PTSD) from witnessing Floyd's murder and testifying during Chauvin's trial.

Williams was also cited in October 2021 for punching a pizza delivery person in the face in Roseville. He failed to appear in court in January and was arrested via warrant but posted bail. His next court appearance in the case is later this month.