A scathing letter sent by the Federal Bureau of Investigation to Civil Rights icon Rev. Martin Luther King Jr. has been uncovered, pulling back the curtain on J. Edgar Hoover’s efforts to discredit the leader as his popularity grew.

In the anonymous letter, published for the first time in the New York Times Wednesday, the author refers to the Nobel Peace Prize recipient as “evil,” a “fraud,” and a “dissolute, abnormal moral imbecile.” The author threatens to expose King as an adulterer and in the end flat-out suggests that the leader commit suicide.

One passage reads: “No person can overcome facts, not even a fraud like yourself. Lend your sexually psychotic ear to the enclosure. You will find yourself in all your dirt, filth, evil, and moronic talk exposed on the record for all time. I repeat—no person can argue successfully against facts. You are finished.”

The FBI under Hoover devoted a great deal of attention to Dr. King, whom Hoover considered a threat to national security, Vox reports. The letter reportedly came to be after Hoover failed to prove King was a Communist, which he could have used to disgrace him. Yale professor of American History Beverly Gage wrote in the New York Times, the letter is “the most notorious and embarrassing example of Hoover’s F.B.I. run amok.”

Read the full letter at the New York Times.

Contact us at letters@time.com.