I don't think a pissed off ex could pull off something like this. Seems like a complete psychopath serial killer that might have killed before or a professional hitman..Someone with ice water in their veins for sure...
I don't see how a normal person who never killed before could snap so bad that they would use a medieval weapon like a knife instead of a gun...A normal person that just snapped would probably want to get in there, do the dirty deed and get out quickly, with as little trouble as possible, and I wouldn't think they would want to take the risk of using a knife when they could possibly get over powered or not know where to hit a person with a knife and possibly leave one of them alive by mistake.
You sure seem to know a lot about the mind of a psychopathic serial killer
