Why do the predators kill unarmed people in AvP?

Why do they kill everyone in the whaling station (at the very start of the movie not when the expedition gets there)? It doesn't make sense. Sure, the pyramid is below the station but the whalers were just doing their job. And in AvP 2 its ridiculous how the main predator stalks and kills civilians for no reason, when it could be hunting the aliens instead. eg when they're barricaded in the gun shop and the predator catches one of them and hangs him from the ceiling for no reason, then leaves. wtf?