Every time i watch this i always think bout carol and the kids like who gonna tell em daddy dead and do you think dave cared for them? Like he couldve not been a little psychopath and lived that white picket fence life but instead lived a double life and it seems like the thrill of the kill appealed to him more.
I do sense a bit of Jekyll and Hyde with Dave York. It's possible he was both loving dad and husband and killer. I'm not completely convinced Dave York is psycho though. His motive for killing Susan is to cover his tracks. If not, there goes his entire life. To me it does look like he loves his daughters. Unfortunately, it's not a Dave York movie. So who knows what he's really thinking. We can only infer from what little we saw in the movie.