Guns and Petals | Sookai

Kai doesn't expect much in life, food on his plate, roof on top of him, and graduated College peacefully. That is all he asked but now his landlord wouldn't hand him the key to his apartment. So he decide to moved in with his best friend.
But he wasn't expect was to walk in with the sight of two men fighting in the living room. Beomgyu and Soobin point guns at each other with bruised faces and bloody noses.

Why did they have guns? And why do they try to kill each other？