Yep.. I'm 20.. now I can look into concealed liscenses in texas..

I'm not dumb, but in this kind of situation I would tell him to back off, and if he proceed, I would let him understand he needed to get back in his car and leave.
It doesn't sound like you did anything, and people that flip like that and just dumb.
*story: (just incase you didn't care to read, it was a warning)
I was pulling out of school , h.s., (before any mods to the car) andthere are basically 3 columns of people that try to get out this 1 exit... Well I had been patiently waiting to leave for about 4 or 5 minutes, all of the sudden this guy in a black mustang comes barelling up to the 'line' next to me, well everyone is going 1 by 1 by 1 in good order. Well, this guy decides that the 2 seconds he has been waiting was enough and is on the guys bumper in front of him.. well me being about order I pull up, of course im not gonna let this ******* get in front just because he is in a 'mustang', and I knew of the guy and he was a **** all the time too..
So I pull into the exit becuase it's my turn, and he punches it, and slams the brakes not to hit me, slams his hands on the honk for at least 5 or 6 seconds while flicking me off with both hands.. well the exit turns into a right , or left and strait. I'm going left, he is turning right. I pull up in front at the light and then so does he, he is mad doggin me.. his girl was ok, but nothin special, especially since he always tries to be a bad ass. anyway.. He looks over, I have my windows down.. so I look over, check out his girl for a half sec (literally 1/2 a second) look back at him smile and waive...
About 3 days later I ran near him in the hall, he goes 'dont talk to me fag', I just smiled and said.. 'sure thing'.
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Point is, people get the feeling they were wronged and take driving TOO seriously. When I have to slam my breaks at 50 to a stop (hoping i dont get rear-ended) becuase of an unsafe left turn, which are unsafe (all 3 in 1 day min you) I just go on about my business..
People get so stressed out driving that they flip.. BTW: it doesn't surprise me a guy like that had his front and rear bumper covers messed up... that's motivation for him to get angry, but it is still incredibly irresponsible to go to that extreme instead of just maybe a honk.