I see this kind of conversation almost nonstop in chat:
Tom: omg you fuckin dick wtf
Tom: hey guys SatanDude is killing people for no reason
SatanDude: you were running around in radtown
SatanDude: and you had 120 ore
Tom: BUT I SAID FRIENDLY
So if you are a new player, here is a simple, effective piece of advice; stay away from the road and towns. There are certain factions of people who will roam or camp the NPC buildings and kill everything on site. There is another faction of people who may be getting harrassed or attacked by others and will kill you because they feel threatened.
You have a much higher chance of meeting someone that is friendly if you are far away from civilization.