What happened to Monolo Conde's two sons and how did their fates inform the community's view of the Witch and the Girl?

After the funeral for Monolo Conde, his two adult sons left together in one vehicle. During the drive, they were involved in a fatal accident. As a result, the community became even more convinced that the Witch had been controlling events with her magic and that she had almost certainly killed her longtime lover's two sons as a means of preventing them from discovering and reporting her role in the death of their father.