 Couple of guys have a brightly burning something in the middle of what looks like a school playground (I think I see swing sets in the background). The one guy is walking back towards the camera with his back to the fire. He is sauntering along looking around when suddently it explodes in a huge bang and fire shoots up into the sky in a mushroom cloud. It scares the crap out of the guy who had his back to the fire and even the camera man ducks down quick. Right after the explosion they both take off running down a tunnel away from the burning whatever it was. Don't try this at home kids.
Watch these two guys set off an explosion and scare the crap out of themselves. Source: Big-boys.com | 
