Thanks to Deon for sending this in.

From the photo above it is a rather straight forward design. It is a pull back sling shot style firing mechanism. The black straps are most likely some elastic probably rubber and they propel the screw driver forward driving the screw driver tip into the back of the round striking the primer. I am a little concerned about how much brass is exposed. I can not tell if the cartridge is fully seated or if the police pulled the round out a bit for illustrative purposes when they took this picture. If it is fully seated, I suspect that round will have an out of battery detonation and explode right into the hand. I do not see a grip of any kind so I think one would have to grasp the entire device and wrap his hands around it to fire it. Bye bye hand.

Upon closer analysis there are rubber bands holding the crude barrel in place. This might allow the barrel to be moved in order to extract the fired round and reload the barrel if this gun can be successfully fired without injuring the operator.