A PFA Radio listener texted me the following:

Druff, I think you are correct it wasn't a drug deal, but there's something you are overlooking.

I think it may have been a GUN deal! Remember BJ is very into guns and has said many times in his videos that he has a ton of them. The guys who approached him admitted they had been at a gun store earlier that day and were denied. Maybe that's what this was all about? Also maybe that's why he drove away to his dad's house after the shooting, to hide the guns he had in his trunk! Just a theory but something to consider!
Interesting theory!

Lots of things fit here. The thing that was strangest to me about BJ's story was that the dude just whipped out a gun and started firing. Why? He hadn't even gotten very close to them yet. Even if the plan was to mug BJ and his girlfriend, wouldn't it be smarter to pull the gun when you get nearby, so they don't run away?

That part of the story didn't set well with me. Secondarily, the running home to Daddy thing -- while somewhat explainable (perhaps he didn't want to wait there for the other guy to come back with friends) -- also seems a bit suspicious for a 40-year-old businessman and gun enthusiast.

If this was a gun deal, perhaps Joseph Smith and his brother Kevin planned to rob BJ of the guns, not knowing that BJ had a concealed weapon on him. Perhaps BJ shot Joseph dead during a robbery attempt of the guns, brother Kevin ran off, and BJ quickly booked it over to Daddy's house so he could hide the trunk full of guns he had.

It would make sense for Kevin to back BJ's story, making him just a bystander for his reckless brother, rather than an attempted robber during an illegal gun sale.

Meeting 15 minutes after In-N-Out closed also makes sense, because they could explain why they were all there if the cops rolled up, yet there was a good chance everyone else would be gone.

The only part that doesn't fit? Would the brother really meet him in the SAME lot where they tried to earlier buy a gun, and threw a rock through the window after being denied?

Anyway, very interesting theory.