Musashi1596: I left him alive because I had no hard evidence to suggest he had been hurting anybody, but had it transpired that he was in fact killing those he ate, then he would have been killed.
Baggins: Well he does have a veritable garden of Echinops just outside of his hut, which he runs to get away from you (and or pick up a weapon). The sign of murder, as we learned in Chapter I.
Good catch!
I'd even add, that he could be quite the devious killer. When Geralt arrives in the swamp, Gramps waits there for someone who will ecort him to the shrine of Melitele, so he can worship her... Since we know that Melitele doesn't like killing anything/eating meat (a nurse at Lebioda Hospital says so!) we have to offer a plant (!) at her altar, so we'll get the three Sephiroth stones. Now my question is, why would a cannibal worship a goddess that specifically doesn't allow meat as offerings?
Isn't it possible, that Gramps only asks people, who arrive in the swamp, for this escort through this dangerous path, so they die on the way and he can eat them? During the whole quest he screams and runs when monsters attack Geralt, but when you choose to fight him he suddenly has an axe and knows how to use it.
Am I reading way too much into this, or does anyone else think I'm onto something?
I'd really love to know what the writers intended here or if it was written this ambiguously on purpose and they themselves haven't decided what's the underlying truth.