Ouch, that story is ugly. If it were me I would have called the Sheriff's Dept. and had them send out a car to check the guy out. That would have made the agent real happy, a nice big fat marked unit pulling up behind him.
I believe the agent should have ID'd himself though, not smart to get into an argument with the homeowner. If the homeowner had the guts to come out and confront the agent, he probably wasn't the type of guy to just go back in his house and forget about the whole thing. But, walking back out with a gun wasn't real smart either.
I'd like to hear some more particulars about the whole thing.
There is plenty of stupidity to go around here, no doubt. If this were a story about two civilians the responsibility would largely be lumped on the homeowner However, the individual in the vehicle was a law enforcement officer, and we expect our law enforcement officers not to be stupid...since it leads to people getting killed.
All he had to do was flash the badge and tell this guy he was on official business.