Killing someone over two batteries is highly illogical.
Yep, that's why the old man was incredibly stupid to pull a gun on someone, over two batteries.
...more than likely he was very desperate. Could have easily been a scenario such as I mentioned earlier.
There are lots of options to get batteries besides pulling a gun on someone.
And if my family was trapped under a beam in a collapsed house in the dead of night is probably pick up a friend and drive on down to the 7-11 to pick up some spare batteries and argue with the clerk about the price....Get real.
You can try and justify it all you want. It's an old man throwing a temper tantrum with a store clerk at gunpoint because he didn't get his way.