From news article:
[g]unmen stormed three D.C. buildings, taking 150 hostages and one life. Today the city remembers that terrifying hint of things to come.
For 39 hours in March 1977 -- before the word "terrorism" entered our daily vocabulary -- 12 gunmen paralyzed the District in a three-point siege. The group of Hanafi Muslims held about 150 people hostage in three buildings, and before they surrendered, a young reporter was killed and dozens were injured, including D.C. Council member Barry. A shotgun pellet pierced his chest, right above his heart, nearly killing him.
The 12 gunmen had several demands. They wanted the government to hand over a group of men who had been convicted of killing seven relatives -- mostly children -- of takeover leader Hamaas Abdul Khaalis. They also demanded that the movie "Mohammad, Messenger of God" be destroyed because they considered it sacrilegious.
Most of the hostages, more than 100, were captured at the B'nai B'rith headquarters.