Explain briefly how Tom was killed. What is Atticus's explanation for Tom's attempted escape?

Tom is shot multiple times when attempting to escape over the fence at the prison. Atticus' explanation of why Tom would try to escape alluded to Tom's hopelessness.

Atticus leaned against the refrigerator, pushed up his glasses, and rubbed his eyes. “We had such a good chance,” he said. “I told him what I thought, but I couldn’t in truth say that we had more than a good chance. I guess Tom was tired of white men’s chances and preferred to take his own.

Tom was shot 17 times while trying to escape over the fence at the prison. Yet Atticus explanation why Tom tried to escape was becasue of the helplessness he felt. Tom mostlikely felt this way because of the chances that was the white folks were giving him.