Player killing is when a player kills another, deliberately or accidentally (lol it sounds like murder.. anyways). PK (or player killing) despite being allowed in Moral Decay, is frowned upon. Now in MD in order to PK someone, a reason will be needed and under no circumstance is it allowed to PK a newbie (a person who is new to MD). It is allowed for someone to PK a secondary character who is low level.

see also, Rules