The deadly sins

Since the day was bitter cold enough,
A man digging grave , for the dead whom
The murder he committed the day before,
The dead cursed him at his last breath,
After a week, a new mystery occurred ,
Same as the death of dead had occurred,
A human body laid on the stairs of the graveyard,
For the sin he had done,
Punished he was for that,
A note written with him the people got,
Written for Mr. Robert, 'THIS IS FOR THE DEADLY SIN HE HAD DONE'.