I'm pretty sure that J.K. never revealed who killed Igor.
When I guessed Severus and it told me that I was "hot" and that the same person killed the person the quiz was looking for, I started naming every possible person who had been killed by Voldemort or Tom Riddle. Even Hepzibah Smith.
I could be wrong, but I also just checked Harry Potter Wiki's Death Page and it says Igor's killer is unknown or "varies." |