After Tom Robinson was found guilty of raping Mayella Ewell, he was sent to Enfield Prison Yard. Atticus hoped that he would eventually free Tom on appeal, and he told Tom to keep the faith. But Tom apparently couldn't stand the confinement of prison life, and he decided to try and escape during his exercise period.
"They said he just broke into a blind raving charge at the fence and started climbing over. Right in front of them--"
The guards called for Tom to stop, but he just kept climbing. The guards told Atticus Tom would have been successful if he'd had two good arms. After firing several warning shots, the guards shot to kill. His body had seventeen bullet holes in it.