If twenty doctor whooves were sitting on your table and one of them killed another with a rock would that be a time paradox?
Good question! I imagine the rock murdering would be a fixed point in time, which means that it was always meant to happen. Or, at least, I think that's what the rock bonker would tell everyone present so they weren't weird about it. It's kinda like how if you get accused of a crime in Star Trek, but you were possessed by an alien, it turns out to be fine.