Then-Detective Joseph Mensah testifies before the Senate Committee on Judiciary and Public Safety in 2025. (Photo by Isiah Holmes/Wisconsin Examiner)

Detective Joseph Mensah, a  Waukesha County Sheriff’s detective who attracted protests and controversy for his involvement in three fatal shootings over a five year period while employed at the Wauwatosa Police Department (WPD) will resign from the Sheriff’s office. Mensah, hired to the Waukesha County Sheriff’s Department in 2021, issued a resignation letter on July 17. In a resignation letter, Mensah said he plans to leave the law enforcement profession all together. 

An version of the letter was posted on social media by Jessica McBride, a contributor to the right-wing media outlet Wisconsin Right Now. Mensah’s resignation will be effective on July 31, according to the letter.

A Waukesha County Sheriffs Department spokesperson sent a slightly different version of the letter to Wisconsin Examiner upon request. “After much consideration, I feel it would be in the best interest of the Sheriffs Department, the community, my family, and my own personal well-being, that I transition out of the law enforcement profession,” Mensah wrote in the letter. “Words can not express how grateful I am that you, Sheriff Severson, along with Inspector Gumm, Deputy Inspector, the command staff, and the Waukesha County Sheriff’s Department accepted me and brought me into your family when I needed you most. I am beyond grateful and thankful, that I had the opportunity to serve alongside the men and women of this agency. If there is anything I can do to assist with this process, please let me know.”

Mensah was hired by the Waukesha County Sheriff’s Department after resigning from WPD in 2020, following months of protests. After he was  hired by WPD in 2015, Mensah was involved in three fatal shootings. In his first year on the job Mensah shot 29-year-old Antonio Gonzales, who was wielding a sword when officers arrived at his home. Less than a year later, Mensah fatally shot 25-year-old Jay Anderson Jr., who was sleeping in his car in a county park. Mensah said that Anderson lunged for a handgun that sat beside him on the front passenger seat. Four years later in early 2020, Mensah killed 17-year-old Alvin Cole, who was fleeing Mayfair Mall with his friends after being involved in a fight, and brandishing a handgun. Mensah said that Cole attempted to shoot him during the chase. 

The Milwaukee County District Attorney’s Office declined to charge Mensah in any of those shootings, stating that his actions were either justified or privileged. 

Residents and elected officials in Wauwatosa called for criminal charges against Mensah for the three shootings. When the district attorney declined to issue charges in the Cole shooting, protests ensued and a curfew was declared in Wauwatosa with  protesters confronted by militarized law enforcement.

An independent investigation found that Mensah violated department policies when he gave radio interviews in which  he discussed the Cole shooting, which was still under investigation at the time, and gave misleading information about his fatal shootings, according to the report, authored by attorney Steven Biskupic. 

Mensah’s three shootings in Wauwatosa also became the subject of several lawsuits. In 2021, a John Doe hearing was called to review the Anderson shooting, after which a Milwaukee County Circuit Court judge ruled that probable cause existed to charge Mensah with a crime. Special prosecutors appointed to the case, however, declined to pursue charges. 

In 2025, Mensah testified before state legislative committees to advocate for prohibitions against the use of the John Doe law to review fatal shootings by police. Mensah told Wisconsin Examiner that he’d sought a promotion to lieutenant while at the sheriff’s department, but was unsuccessful. 

Another federal civil lawsuit involving the Cole shooting was brought to trial, and a judge found that Mensah and other officers provided contradictory statements. Wisconsin Examiner also found that Mensah and other officers violated policies related to police shooting investigations in the Milwaukee area. The Cole trial in 2025 ended in a hung jury, with a retrial scheduled for early September. 

In a statement to Wisconsin Examiner, a spokesperson for the Waukesha County Sheriff’s Department said that agency staff “support Detective Mensah and wish him the best.” 

Attorney Kimberley Motley, who has represented the families of those killed by Mensah and the protesters who supported them, said in a statement to Wisconsin Examiner that the Cole family “is looking forward to the trial that is set in September against Joseph Mensah. Both the Alvin Cole and Jay Anderson family continue to focus on fighting for justice on behalf of their loved ones.”