From start to finish, it was impossible for monsters and NPCs to coexist peacefully. Thus, from the moment Zhou Tian identified these NPCs, he saw them as his enemies. Zhou Tian has never been soft on his enemies. This being the case, it wasn't strange for him to unreservedly attack the NPCs once he decided to make a move.
After all, killing NPCs did have certain benefits. Although Zhou Tian only needed to forcefully take some magic crystals and then he could leave, other factors motivated him. Coupled with the fact that he had been frustrated for some time, he saw this combat as a way to vent. Under such circumstances, Zhou Tian was ruthless against the NPCs.
As such, Zhou Tian didn't know how many NPCs he had killed along the way. But when he eventually took full control of the mining area, there was not a single living NPC left there.
