In the early morning hours of Dec. 4, 1969, Chicago police—acting at the behest of the Cook County State’s Attorney’s Office and the Federal Bureau of Investigation—burst into headquarters of the Chicago Black Panther Party and rained a hail of gunfire. When they were done, chapter founder and chairman Fred Hampton, 21, and member Mark Clark, 22, were dead; four others were seriously injured.

The police lied and said that when they knocked on the door and announced themselves, the Panthers immediately began shooting at them. This was later proven to be a lie. A federal grand jury found that the police had fired somewhere between 83 and 90 shots. The Panthers had fired maybe one, and the grand jury said that shot was fired by Mark Clark after he had already been shot in the heart.

It was ultimately revealed to be a massive coverup that was part of a larger federal attempt to dismantle the Black Panther Party from the inside with a program called COINTELPRO.

COINTELPRO or the Counterintelligence Program was an initiative started by the FBI in 1956. It used covert and often times illegal methods to disrupt the activities of groups it saw as a threat. Initially used to attempt to stop the Communist Party, in the 1960s COINTELPRO targeted domestic groups that included the Black Panther Party and the Socialist Worker Party.