I hate to say it, but, did they know each other? Was there any other kind of illegal activity/relationship between the men prior to this? Why did the home invaders select this particular home?
Probably just selected the home at random and the homeowner righteously protected himself, but sometimes questions are raised.
9 times out of 10 it’s a drug/cash connection.
Or, it could have been a man protecting his family from violence.
Even Freud recognized that sometimes a cigar is just a cigar.
This is always the first assumption that cops make about a home invasion case, and the first thing that they look for during the investigation. They often find something too, but not enough to press further charges.
Then again, there are cases where a person innocent of any criminal connections gets picked out by armed robbers for an home invasion.
Either way, dead robbers are an ultimate deterrent measure.