Carpools and Trucks

I had a questionable morning.
Besides having a questionable interrogation from another carpool mom...
I yelled at a truck driver in the carpool parking lot.
His flatbed semi was taking up THE WHOLE parking lot where carpool drop is. His truck was turned off, so I parked behind him. The spot where there was room for my car. Mid switch of children into the carpool car the truck suddenly sputters to life and starts reversing. There is about 5 feet between the back of his truck and my car. I push my daughter towards the carpool car and start yelling for her to get away. But she follows me. I am yelling trying to get my car on, and moved before the truck crunches my car. I move my car a couple of feet, and his truck stops.
I get out, and walk over to the truck driver and just let him have it. A 10 second stream of "what are you doing, there are children behind your truck you ass!" But, I should have never parked behind a semi-truck my inner wisdom is calmly whispering in my ear....
He gets out and tells me he needs to move his truck.
"When I am done, I will move my car" I say.
But I kinda yelled it.
Meanwhile M. had gotten in the carpool car.
We all shut our doors and are on our separate ways.
I am feeling sick inside though.
Ever have a situation you wish you had handled differently? Today was that day. M was out of my sight for some seconds while I was getting the car moved. That means she could have run behind the truck if she was confused. That is weighing so heavily on me. That I was so concerned with moving my car and thinking she would follow my directions to go to the other car, but really she heard me yelling and got scared and sort of froze not knowing what to do. This was a 25 second event, but I am questioning all aspects of my mothering skills at this moment. Sucks. Sucks bad.