This is so not me... how did this happen?

I went to the mall this morning to do some walking, and to get a few things that I needed. I get there before the stores open, walk around until they do, jump right in and get what I need without a wait or any people around. It's great. Melody tried her best to be good in the stroller, but she was getting a bit cranky towards the end and just wanted out. So I was a little frazzled as I was leaving the mall. I'm walking to the parking lot and I see a woman in a GIANT car parked next to me with all of her doors open, bags everywhere, and 2 kids in the stroller. I walk over to the car, put Melly in her seat, unload all of my bags, put the stroller in and hop in my car. I look and the woman had the back door open next to my car so I wait a minute until she closes it and walks around to the back of her car, then I start my car. She starts freaking out yelling at me "You could at least f-in wait until I'm done!" So I get a bit bent out of shape (I was frazzled) so I roll down my window and quite sarcastically say, "I didn't realize it was a crime to start a car in a parking lot". She gets all uppity and screams "You just pumped exhaust fumes all over my kids, you should have waited until we were done". I had assumed that all of her opening and closing of the doors while I was putting Melody into my car was her putting her children into her car, not keeping them in the stroller while she safely tucks away her bags of shoes. So, because of this, another side of me comes out and says, "Maybe next time you should actually put your kids in the car first and a little faster then". And I drive away. I was really worked up. I never get worked up. I'm the opposite... to a fault sometimes. This really came out of nowhere and really got to me. Obviously this was the other woman's issue. I think what hurt me the most was that this terrible woman would think that I would ever put a child in any harm. The even scarier part is that her kids are listening and watching every move she makes, and are learning all of her bad things. Maybe that's why it got to me so much. I was so worked up and I don't want Melody to ever learn to do what happened at the mall today. Well, except that there are just people in the world that you're better off just ignoring instead of rolling down your window to get them all uppity!