I wish John didn't make Percy kill Wild Bill
I know he deserved it, but he was already on death row, so what was the point? The point of John's character is that he couldn't hurt a fly, but he basically becomes a murderer.
shareDon't forget that Wild Bill grabbed Percy through the bars and basically assaulted him, kissing him on the temple and fondling his private parts and suggesting icky sexual desires of what Wild Bill would love to do to him, and Percy was so terrified he wet himself and was further humiliated by the other inmates laughing at him, whom he had just hurt himself (causing Del to fall down when he tripped).
I'm tempted to think that Percy was indifferent to the fate of the two girls (at best), but whether he was shocked by Wild Bill's crimes when John showed them to him, it's not clear (would Percy tear up for dead girls?) but I think Percy shot Wild Bill for humiliating him, especially justified that Percy could've been Wild Bill's third victim.