A Michigan police officer is under investigation and on paid administrative leave after potential buyers of his property toured his home and found items inside related to the Confederacy and the Ku Klux Klan.

Robert Mathis, who is black, and his wife, Reyna, toured the home of Officer Charles Anderson, a member of the Muskegon, Michigan, Police Department. On the tour they were confronted with multiple Confederate flags, and a framed document in one of the upstairs bathrooms.

That old, yellow paper turned out to be an application to the Ku Klux Klan.

“There’s just this one plaque on the wall, so I walk over to the wall and take a closer look, it said it was a KKK application,” Mathis told NBC News affiliate Wood-TV. “I said, ‘I want to get out [of] here right now.’”

Mathis quickly left the property in Holton, Michigan, he said in a Facebook post with an image of the photo. The post has since been shared thousands of times. One of the people who saw the image alerted Muskegon city officials, Wood-TV reported.

Since the discovery, the police department placed Anderson on paid administrative leave pending an investigation.

After seeing the items in the house, Mathis told his realtor that he would not make an offer on the house and felt "sick to my stomach knowing that I walk to the home of one of the most racist people in Muskegon hiding behind his uniform and possibly harassing people of color and different nationalities."

“To know that I was walking around on property associated with some type of racism, some type of hate, when I got outside I felt like I needed to be dipped in sanitizer,” Mathis told Wood-TV.

Anderson was not able to be reached for comment, but his wife Rachael Anderson denied that her husband was a Klan member. She added that while they couldn't say anything now, "I wish we could because it would probably set a lot of things straight."

That will not be Anderson's first experience with an investigation.

He was previously involved in an officer-involved shooting investigation, according to Wood-TV, after he shot and killed Julius Johnson in September 2009 after a routine traffic stop. Jones was a passenger in the car, when the driver suddenly pulled away.

Anderson shot Johnson after the two fought in an alleyway. He later told investigators that he feared for his life.

Wood-TV reported that Johnson's sister, Tunisia Phillips, told investigators that she heard her brother beg for his life before the shooting, but prosecutors found this to be untrue and charged her with lying to police. She served three months in jail.

Though the NAACP at the time called for a federal investigation, one was never started.

The discovery of these items in Andersons's home now coupled with that previous shooting is concerning, Muskegon County NAACP’s President Eric Hood told Wood-TV.

“We want a thorough investigation to be sure that when he goes out there and puts on that uniform and performs his duties as an officer that he’s being fair and impartial,” said Hood, who is also the vice mayor of Muskegon.

Muskegon county prosecutor D.J. Hilson said he didn't think the recent discovery would change the outcome of the 2009 investigation, but he would follow the evidence wherever it took them.

“We have a legal moral and ethical duty to not only substantiate that new evidence but to further investigate if it shows that in fact there might have been a different outcome, had that evidence been known,” Hilson said.