The Oakland County Sheriff's Office terminated longtime employee Sherry Prose last month after she posted the Halloween/election-themed photos ... with the horribly racist twist.

The sheriff's office says ... "These types of incidents are disgusting and will never be tolerated or pushed aside at the sheriff’s office." It adds that behavior like this "brings tarnish to the badge."

It's unclear when Prose shared her post, but it featured 3 pumpkins in one photo with the caption, "Trump, Biden, Pence and Kamala. Happy Halloween." The second photo shows Harris as a watermelon jack-o'-lantern.

Prose has reportedly worked in law enforcement since 1994, and insists she's not a racist. She says, "I worked hard in my law enforcement career and I am proud of the reputation I earned in my 30 plus years of service. I am not racist and never will be." She never explained the photo, though.

Rev. Dr. Wendell, president of Detroit’s NAACP branch, points out that the watermelon correlation with Black people is "linked to buffoonery and to less than." He adds ... "I believe that the intent was purposely structured to diminish and to dilute the significance of the first African American ... as Vice President of these United States."