it should be explained clearly or added to the tutorial in some way?
Yes this would be good! Many other games DON'T have friendly fire, so people who don't know anything about DnD 5e (like me!) but know other games, won't be quite so shocked and surprised the first time they kill their own party.
Then again, in my first ever battle as a Combat Archer in the SCA, I managed to kill my own Queen by accident... WHOOPS... how's that for friendly fire...
