I'd say 80% of males are emotion bottlers. It would have to be a very strong internal reaction to cause him to actually murder two other people.
Standing there with your fists clenched and your eyes closed is different than actually approaching someone with nothing but rage.
If you've ever actually gone at someone, I mean really just gone at someone, rage can take control in a moment and it won't let go until something else snaps or it simmers down and fades away. I can't see any strong reason to go at elderly people though. That's the bizarre part.