Jackson was convicted and imprisoned as a felon at age 18.
On January 13, 1970, along with two other inmates, he was charged with killing a guard in retaliation for the murder of three black activists at the California's San Quentin prison. He was incarcerated in the maximum-security cellblock at Soledad Prison. Jackson and the other two inmates became known as the "Soledad Brothers."
August 7, 1970, George Jackson's 17-year-old brother Jonathan burst into a Marin County courtroom with a machine gun, freed three San Quentin prisoners and took Judge Harold Haley as a hostage to demand freedom for the three "Soledad Brothers." However, Haley, prisoners William Christmas and James McClain, and Jonathan Jackson were killed by police fire as they attempted to drive away from the courthouse. The case made national headlines.
Isolated in solitary confinement for 23 hours a day, Jackson studied political economy and radical theory and wrote two books, Letters from Prison and Soledad Brother, which became bestsellers and brought him world-wide attention.
On August 21, 1971, Jackson was gunned down in the prison yard at San Quentin in what officials described as an escape attempt. In his possession, he had a 9mm automatic pistol alleged to have been smuggled into the prison by Angela Davis.