Mom flips off another driver while driving, guy makes passive threats.

[solids]

First things first, tell your mother to grow the [censored] up. What she did was pretty juvenile and dumb.

As for you, I'd just let it go, as his threat seemed pretty idle. He was trying to [censored] with your head and get you all paranoid, and it seemed to have work. Give him props for successfully ninja-ing your brain, and move on.