Was it just an innocent family having dinner or whatever, minding their own business and fortunately armed and prepared?
Or was it someone he might have had knowledge of, involved in... whatever nefarious activity that he intended to catch by surprise?
Maybe a poker game with lots of money on the table or something like that.
It was three other young men of about the same age, and when they broke into the apartment, a gunfight commenced. My guess is it was drug-related.