Good thinking.
A charged high voltage, high energy cap with one lead grounded should do the trick nicely and could be surreptitiously deployed there.
Yes, it would kill someone quite handily and I do not suggest you do that as it is against the law and all that jazz.
Damn, they don't let you do anything fun these days. No wonder those young'uns are addicted to their pokemans and instagrams.
Edit: Love jazz but hate the law. Just kidding, hate jazz too, maybe more than the law.