The investigation will determine whether the organization should be stripped of its role as the state's official advocate for people with disabilities, the Milwaukee Journal Sentinel reported Friday.
The report found that doctors at the psychiatric hospital failed to provide basic medical care, leading to the deaths of four patients in 2012. It was written by psychiatrist William Knoedler and was based on patient records that Disability Rights Wisconsin had given to him.
Knoedler called Walker's decision to investigate the rights group "an utter deflection of responsibility."
"Clearly, they care more about their own embarrassment and looking for ways to divert attention than they do about patient care," Knoedler said.
Disability Rights Wisconsin gave the report to state and federal officials, County Executive Chris Abele and two county officials last summer, but did not release it to the public or share it with the county board.
The Journal Sentinel wrote about the report in January.
Milwaukee County moved to discredit the group, and asked Walker to investigate the agency. The Journal Sentinel reports that Walker assigned the review to state Department of Health Services attorneys on March 12 and notified the county of the move this week.
The investigation was first reported Wednesday by Milwaukee blogger Chris Liebenthal. He is a human services worker for the county in the same department that runs the Mental Health Complex.