Your question me is unknowable. I do not know what they might have otherwise done.
It IS knowable. These criminals broke into his home before (how many times we are not told yet), and the house was broken in at least 8 times by other teens (which may or may not have been friends of the criminals that are now dead), so if they were willing to break the law multiple times to steal his weapons, you don’t think they’d want to exact revenge if they got off with a slap on the wrist a a bullet in their ankle? you’re pretty naive to think that as I KNOW they’d come back and wanting more than more of his guns, they’d want him dead. PERIOD.