Question: The Brink's robbery of 1981 was an armed robbery and three related murders committed on October 20, 1981, which were carried out by six Black Liberation Army members, including Mutulu Shakur, he was a close friend of who?
Sentence (from "Brink's robbery (1981)"): The Brink's robbery of 1981 was an armed robbery and three related murders committed on October 20, 1981, which were carried out by six Black Liberation Army members: Jeral Wayne Williams (Mutulu Shakur), Donald Weems (Kuwasi Balagoon), Samuel Brown (Solomon Bouines), Samuel Smith, Edward Joseph, and Cecilio "Chui" Ferguson; and four former members of the Weather Underground, now belonging to the May 19th Communist Organization, consisting of David Gilbert, Judith Alice Clark, Kathy Boudin, and Marilyn Buck.
Relevant evidence: Yes