This was my friend's first outdoor sport lead. He clipped the first bolt fine, then went on the clip the second bolt but I noticed that he was away to z-clip. So I started telling him not to clip that way, he dropped the rope and then fell. The first bolt took some of the force but somehow the quickdraw unclipped from the bolt and he fell to the ground. Luckily he wasn't too high up yet and the first bolt took some of the force so he was fine. I know rope can unclip from quickdraws if you backclip, but I've never seen a quickdraw able to unclip from the bolt in the wall! Must have been from the attempted z-clip pulling the quickdraw up or something.