User blog comment:IamJakuhoRaikoben/Chapter 431 & 432: My sword is... & Brair in Love, Review./@comment-25334245-20150428225357/@comment-7418318-20150429194019

With Gray's comment about not being like those killers (or murderers depending on the translation) I doubt they could have made him kill Frosch in any other way than using Mr. Cursey, so my money's on either that or an accident/friendly fire.