I'm not going to lose any sleep over this but I'm not the murdery type and was quite happy to never get that achievement. But I just did courtesy of the recent sorc pet changes.
I was in a questing area I'd taken another character through recently and flung an attack. But it was one of those area where there are civilians at first and the bad guys only turn up later. So I backed away, content to either run or die but I couldn't unsummon my pets and they killed my poor victim. Bit annoying.
Though now that I am flagged as a murderer, no point in holding back...