Wesley Cook established his status as a political activist while still a teenager. At age 14, he took part in a protest against a rally for presidential candidate George Wallace and was subsequently arrested by Philadelphia police. The arrest did not deter him from further political activism, and in 1968 he became one of the founding members of the Philadelphia chapter of the Black Panther Party, committed to African American empowerment and self-defense. He briefly worked at the Black Panthers’ newspaper in Oakland, California, in 1970 and returned to Philadelphia a short time later. He also legally changed his name to Mumia Abu-Jamal in 1970.

Both in print and on the radio, Abu-Jamal repeatedly criticized the Philadelphia police department as well as the administration of Mayor Frank Rizzo, a former police commissioner, for what he alleged was systemic racial bias and police brutality. He was especially critical of the police department’s handling of MOVE, a radical black-liberation group based in Philadelphia. In the early 1980s Abu-Jamal was the president of the Philadelphia chapter of the Association of Black Journalists, and his news broadcasts and commentaries were heard on numerous radio stations. Because of his activism and radical viewpoint, however, Abu-Jamal struggled to make a living in journalism. To earn extra money he began working as a night-shift taxi driver.

According to his own account, in the early morning hours of December 9, 1981, Abu-Jamal was driving his taxi when he saw that his younger brother, William Cook, had been pulled over by Philadelphia police. There are conflicting claims about what happened when Abu-Jamal got out of his taxi. The following sequence of events, however, was accepted by the jury at Abu-Jamal’s trial: William Cook assaulted Officer Faulkner during the traffic stop, and, consequently, Faulkner attempted to control Cook, at which point Abu-Jamal got out of his cab and shot Faulkner in the back. Though wounded, Faulkner was able to return fire, leaving Abu-Jamal