This is a weird, weird bug. Over on the PTRs, Tig has found that every time he tells his pet to drop the Kill Command, the mob attacked also executes the spell on its target. For example, if Tig is shooting a murloc, and his pet Ganjii is in melee with that murloc, Ganjii's Kill Command will attack the murloc, and then the murloc will somehow also drop a Kill Command attack on its target (in this case Ganjii).

That's a big bug, because if you move it to, say, a boss, a Hunter could drop the Kill Command on the boss while the main tank's health is low, which would cause the boss to instantly attack the main tank, in effect wiping the raid. Not cool.

Hortus wonders if it's just against specific mobs, but that's the last we hear of Blue-- there's no confirmation that it's a known bug and that they're planning a fix. Of course, it is the test realm, so let's not get too excited-- chances are that by the time this big patch reaches the live servers, this won't still be happening. But if you happen to be hitting the Kill Command with your pet on the test realms, watch out for that extra attack.

Thanks, Colin!