There are many interpretations. But the most likely of them is that
Nana patekar turns to revenge and starts killing wolves in sheep clothing. But during this process he does two crimes that really makes him a bad person. First he kills the mad prisoner and next is to help spreading a lie of the prisoner who kills. This lie even made an innocent man being beaten by the police. Nana couldn't forgive himself for what he did, so he made sure of killing himself as repentance of his evil deeds. This is also in parallel to his deeds being done as perfect crime ever done by a man. The secret of him as a killer went with him, not known even to his brother.