I can't find it now. But there is evidence of cheating. The 11 ball is evidence. There is no evidence that that balls were tampered with, but the fact that all of the Pats' balls were deflated and the Colts balls weren't (if true) is enough for him to act.
I don't want him to do it. I just know that Goodell can't just say that they have no evidence and not punish the Pats. It is not going to happen. Anything short of a permanent ban of Belichick will draw criticism. No punishment especially after Ray Rice, will be a disaster.