HE WAS BORED. Also Mitchell has this like . . . the conversation before (or the one before before) was Mitchell being like WELL WHY HAVEN'T YOU KILLED ANYONE IF YOU LIKE KILLING. And he was just like :T. Because Mukuro has told Mitchell that he killed people/hurt them for fun. So it's sort of an on-going project to back that up :') So it is round about provocation.

. . . also he wonders if he can make Mitchell snap '-'b

HOW DOES FERRIS FEEL ABOUT TEAMMATES BEIN' GONE