Jimmy knew what Tommy did. He didn't know know but he knew. He knew it the way some parents know their kids are in trouble fifty miles away or the way the tourists that wandered into the neighborhood knew they should take a u-turn when they saw the Donnellys.
Jimmy knew and it killed him.
'Cause anyone else would've been dead already. He would've crushed their legs before smashing their head in. He would've taken all that pain he felt and let it out on the schmuck who broke him in a way nobody ever expected. But the problem was that it was Tommy…and every time he looked at his guilty face, he saw the first baby his father put in his lap.
Bobby Donnelly had said, "You gotta be careful with him, Jimmy."
And when he lay on the hospital bed pretending to be asleep, Tommy had said, "I love you, Jimmy," like he wanted to run over his heart like he did his leg.
You see, Jimmy loved Tommy too. And he hated him. And he hated himself for loving and hating him.
So, really, Jimmy was stuck. He couldn't let it all out on Tommy. He couldn't hurt him like that.
Maybe that's why he hurt himself instead.