No, the Kid and the whole family was the target, I feel sure. He would have shot more people if they were in the immediate foyer. I don't get why he didn't enter the house and seek her out, then it occurred to me, he didn't intend to kill her, He planned to destroy the one thing she cared about, her family, so he killed her either way, metaphorically.

I know that feeling of unmitigated rage. It's the most miserable feeling in the world. The worst thing evil people do is turn you on yourself in the end.

You can only take so much before you become bitter. If you are strong enough you lash out and he did. He was likely unhinged for years.