The cobra.

(A snake ate my pet bird, when i reached home from school at class 8, i saw the brutal incident and cut the snake into 4 pieces then removed my pet from its intestine ) : Yesterday in my dream one of the snake catchers met in the jungle, He tried to help a cobra from being stuck in a bill, when i reached there he told me to go away from here because i killed a snake brutally years ago, so it may cause you to bite me because of my bad karma. I just replied,,, that day my pet bird was also dead and i just took the revenge.. Then i also joined him to help the cobra. But how does he know about it?