STOUGHTON, Wis. (AP) -

Police in Stoughton say they are investigating a threatening letter that was sent to a black teenager, with a photo that depicted him as the victim of a lynching.

The Wisconsin State Journal reports that the letter had a Madison postmark and contained a photo showing two men hanging from a tree, with a mob watching. A picture of the 18-year-old was superimposed onto one of the men.

Police say in a statement that "this type of behavior will not be tolerated" and the person or people responsible will be prosecuted. They are investigating with help from the FBI, state crime lab and U.S. Postal Service.