I suspect his girlfriend blew through most of his money then left, perhaps going overseas because she feared him or just wanted to be far away now that she was done with him. Perhaps this is what caused him to want to take himself out in a huge way. Killing other people (and if he was a lefty, then he’d want to kill those on the right) seems to be something bizarre that is done to make someone “pay”.
That’s a very interesting angle. Hadn’t considered a breakup due to her blowing away his $$. Then, she up and runs away to another country out of fear. In his unbalanced state, he reserves the room at the hotel in her name (unconsious wish to get her back?).
As good a bit of speculation as any!