It is a sad and serious thing. This is probably the hardest. You will try to convince yourself that you're not engaging in gossip, but are just trying to sort out what happened. Allow God to show you areas where you need to grow. Ask God for wisdom in applying lessons to your life from the mistakes of the fallen leader.
Wrong attitudes proceed the obvious sin.
You may realize that the fallen leader had been quite prideful. Perhaps he thought himself above temptation and carelessly put himself in situations that would easily lead to sin. Perhaps he was not accountable to anyone else. Perhaps he had a temper that he had never learned to control. Perhaps he had neglected his family and almost destroyed his relationship with the wife of his youth.