Why I have no cute home movies

This is a common occurrence in our house. Today, Grant and Ben decided to play and wrestle each other. Ben laid down on the floor, and Grant tackled him, Ben rolled over and they both ended up in a heap, giggling in that little toddler boy way that is the sweetest sound in the world. Then, Grant laid down and Ben tackled him. It was the cutest thing, them taking turns and playing so nicely, every time ending up in a heap of giggles. I decided to whip out the video camera. I hid in the kitchen, so as not to disrupt the game, and started to record, just as Grant laid down, and Ben smacked him in the face. I guess the game changed somehow? Why is it that every time I get out the video camera, stealthily as I can, and I swear they don't notice, everything turns to violence? These kids are going to grow up watching home movies, and thinking, "Wow, we sure beat each other a lot, why did Mom just record it all?"