First video that apparently captures Israel's hyped "roof-knocking" technique--"warning" Gaza home dwellers, with a small explosion up top, that their house is about to be obliterated. Amnesty International has condemned this as an effective warning. In the video you'll see the first small blast and then the massive missile strike. Some have pointed out an edit that makes them appear closer together. More likely about 15 minutes passed. Still, a graphic display.