User blog comment:FairyRaven/Fairy Tail Chapter 344: Wizards vs. Hunters, Review and Commentary/@comment-7418318-20130719181316/@comment-115.133.205.90-20130720131439

Do you even read the story, F. Rogue mentioned that he fell into darkness after Frosch's death, that's why he killed Sting and start his plan on the Dragon Manipulation.