User blog comment:FairyRaven/Fairy Tail Chapter 429 & 430: Code Blue & Purification Ritual, Review and Commentary/@comment-5006572-20150420142523/@comment-4829046-20150420142958

"That filthy liar."

Not really. He never explicitly said the circumstances, just the way he observed. For all we know, Gray momentarily lost control over his demonification and attacked Frosch against his will. Maybe all he did was destroy something and the debris landed on Frosch(shout-out to Nick) and he was unable to do anything before he possibly died.