Kalacha

I only just bought this game recently and my first 3 hours of the game was non-stop being player killed. But after learning how to play the game I started to get my bearings. I will admit I've killed an unarmed guy, and yeah I instantly regretted it. But what about those times were you have to shot? What if the kill was fair game? For example me and a buddy were sitting inside a castle waiting for another friend. He meets up with us but we spot a guy on the tower overlooking our position. We didn't know if he had seen us and with the high-ground he had a pretty good chance at spotting us/ killing us. So we made the decision that we had to kill him to save our own. I creep up the tower and killed the guy, but hiding in the corner was he's buddy which we didn't spot. I nailed him before I was Swiss cheese. I believe that those 2 kills were 'Fair Game'. If there were some negative effects to killing someone you would have to have a system to determine what's murder and what self defence/Fair game. I don't want to wait an hour for killing with a valid reason.