Drunk driving in the parking lot

So, I'm going around the spiral exit ramp of the Smart Park on 4th and Alder in Portland and when I get to the bottom, there's a guy in front of me from Arizona already at the ticket window. He's pulled too far forward and can't reach the window to pay, and I know he's going to back up, so I stayed back farther than I normally would so he could move back. This guy turns out to be WASTED and ploughs into the front of my car! What a moron. So, my mother, who was in the passenger seat, jumps out and tells the guy, who had stumbled out of his car, to move forward so we can see if there was any damage (there wasn't). He stands there and mutters some sort of apology and finally gets back into his car (which at that point I'm thinking is a BAD idea) and moves up a bit. No harm, no foul, but I'm ticked because I know this jackass is going to drive off and he really shouldn't be driving at all. I called the police and reported the drunk driver (mom caught the license plate number) and got mom to the train station in plenty of time, but I was still a little shaken. The only thing I wanted to do was get out of the car and not drive for awhile. Thank gawd for tiki lounges....