User blog comment:Omega natsu2/Chapter 400: Wings of Hope, Predictions./@comment-24066070-20140910141753/@comment-24053170-20140910175303

Actually I believe this is exactly how frosch was supposed to die and why Rogue swore to kill Acnologia, it also explains why he was unable to protect him. Meaning the author had already planned out how he was going to kill off frosch from the start...