Wow. If a movie had someone like this as it's villain I'd roll my eyes at how cartoonisly evil the character was. Im annoyed that such people actually exist.
That is what seems weird to me too. Did he like make a checklist of all the things bad cartoon villains do and is now going through it?
Because his actions just don't make sense. Taunting the family? If this had been race related or religious or something like that I could understand it, but this sounds like he was just some spree killer with no clear ulterior motive.
That T-shirt with "killer" on it? That is something straight out of bad cartoon. (Or that live-action batman series.)
Seriously, all I get is "This guy wants to be the ultimate cartoon villain."