I'll be interested to see if the ex-girlfriend ever comes forward/is revealed to see what she looks like. I have a theory (especially based on the time frame) that if the victim resembles his ex-girlfriend, he formed the intent to kill her while they were sitting there talking at the bar and this was some sort of revenge fantasy. very sad and very disturbing.
Welcome to Ws counselorcurious!
Thinking that your theory will likely prove to be correct, imo.