The City of Muskegon released a more than 400-page report on Monday that includes transcripts of interviews with Anderson and the man who posted images on social media that spurred the investigation, Robert Mathis.
Reyna Mathis, the realtor and Anderson's colleagues were also interviewed for the report.
Anderson, who had been with the department for more than two decades, denied ever being a KKK member or supporter and said that the Confederate items Mathis saw in his home are a "very small part" of an extensive collection of "Dukes of Hazard” memorabilia he has spent decades gathering, according to the report.
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Anderson said the unsigned KKK application from the 1920’s is a historic item, purchased from a vendor in Indiana and collected as part of his interest in American history and antiques.
The report includes an executive summary written by Muskegon Police Chief Jeffrey Lewis that concluded that some community leaders indicated that they had lost faith in Anderson and in the entire police department as a result of Anderson's actions. The City of Muskegon has a population of about 37,000, according to census data.
The executive summary noted two citizen complaints against Anderson that the department was aware of. One from 2010 alleges Anderson "acted rudely and disrespectfully" during an incident which led to the use of pepper spray and two people being arrested, the report states. A second citizen complaint from 2016 involved a DUI arrest in which Anderson did not secure a vehicle after the arrest and did not return a person's driver's license, according to the report.
The citizen complaints were investigated by the department and Anderson was exonerated in both cases, the report states.
The inquiry into Anderson unearthed new complaints made against him that Lewis said will be investigated, according to the report.
The report also details a handful of encounters between Reyna and Robert Mathis and Anderson, including a 2008 incident in which he pulled them over for speeding. The report states they refused to comply with Anderson’s commands and Reyna Mathis "struck him in the face and eye with her hand." Reyna Mathis was sentenced to 60 days in jail for assaulting an officer, the report states, which she disputes.
She told NBC News on Monday that she was defending herself against Anderson in that incident and that when her lawyer asked to enter the dashboard camera from the police vehicle as evidence, the department was unable to locate it so she was placed on probation. She said she only realized after the report was released Monday that the officer she was accused of assaulting was Anderson.
Reyna and Robert Mathis said they believe the department tried to tarnish their images to make Anderson look good and as if the couple was seeking revenge after 11 years.
"This whole situation is very disheartening," Reyna Mathis said. "I feel as though we are being punished because of something we saw in a home that we never asked to see."
Still, the couple said, they have no regrets in reporting what they witnessed.
"We would not take back what we’ve done no matter how we’ve been treated or portrayed," Reyna Mathis said.
Neither Anderson nor the officer’s union, the Police Officers Labor Council, could immediately be reached for comment Monday.
Janelle Griffith is a breaking news reporter for NBC News.