I had the same problem, it WAS a Coon. Past tense due to a .380 auto hollow point. But if this is not feasible go to you're local farm supply and buy a K-9 Electric fence controller by Zareba.
www.zarebasystems.com it works on Coons and Deer. I had deer in my pumpkin patch and saw a doe come off the ground when she got hit. The box charges a wire that works like a capacitor, it holds current until it is discharged, the the box re-charges it.