To kinda copy what others have said I wouldn't be surprised to find out the homeowner is someone who used to sell drugs. Its odd to get 4 guys rich enough to own the Audi and have what to me looks like an AK and other handguns want to invade a house.
And from what the story said is they waited for the man to come home, which I dont get, unless they wanted to hold him so they could get info out of him. Knowing he wasnt home why didnt they go for an entry of some sort then. So that adds to the homeowner himself could have been what they were after.
To me someone, like my father, who has been a hard working straight guy his whole life, and has never had alot of money, would not attract 4 guys semi organized to wait for him to come home to break into his house. If he was to be a victim I am sure it would be one guy looking for something to pawn that will break into his house, when he would be at work or away. The chances of a BG breaking in when someone is home is slim, and then at most times it is an accident on the BG's part.
Thats my 2 cents