Oh yes. I'd rather not imagine what would happen to someone who tried to govern them from outside their own ranks. Not that they're hesitant to involve themselves in the affairs of mere mortals.
It's not terribly common where I'm from either. Those with the ability tend to go a bit mad without proper training and there are only so many graduates from their academies.
Why were they killed? Was it the crime of being different? That does seem to happen an awful lot. Fear of that which we don't understand leads to hatred, leads to violence, and all that.