"STOP! Move your vehicle off the road if possible, especially if it may
cause other crashes."

That was what the drivers manual in my state said what to do during an accident. If I had read that section before, I must have not interpreted it to mean the parking lot of a store. I actually didn't think about the specifics at all nor did the manual mention what constitutes "off the road." And so, I misinterpreted what the other driver was doing. I thought he was leaving.