Report: Broncos investigating racist, threatening letter sent to Marshall

Denver Broncos security is investigating a threatening letter sent anonymously to linebacker Brandon Marshall, Allison Sylte of KUSA reports.

Marshall shared an image of the letter, which is full of racial slurs and violent threats, on his Instagram account Friday.

"Your time is coming, watch out (obscenity)," the letter reads. Later, the sender threatens to "make you an invalid in a wheelchair."

Marshall alerted team officials after receiving the note.

He also told reporters the letter was placed in an envelope with a return address marked as "Mrs. Jackson's Sixth Grade Class" and a note on the back that read "we love you Mr. Marshall" to further entice him to read the note, Jeff Legwold of ESPN writes.

Marshall drew criticism from some when he chose to join San Francisco 49ers quarterback Colin Kaepernick in kneeling during the national anthem out of protest. Marshall announced last month he will resume standing.