Problem w/ Imp from exploding Grotesque

Last night on my Wizard (using Electrocute) I killed a Grotesque, it exploded releasing the three Imps as it should. However, one of the Imps did not function as intended. He stood in place w/ an idle animation, I could not target him or damage him.

I'm not entirely sure if he had been killed and just didn't collapse as he should or if this was a graphical bug. I'm also not sure if I originally damaged (or killed) him w/ a branch from Electrocute, but if I took a screenshot on my home PC. I'll try to post it if you need additional information.