Looks hoaxy to me.

Come on, people. First, verify. I've seen the photograph, and, quite aside from the backwards "B" -- does the surveillance camera show an upside down attack? -- the scratching looks too even and shallow to seem like the result of a violent attack.

And even if it did happen, what would it mean? There are violent attacks all the time, for all sorts of reasons, and if you want to assert that they say something about anybody other than the attacker, you'll need to prove that too.

Bottom line: This is the stupidest distraction in the whole history of this crazy campaign season.

ADDED: I have a bit more to say here.

UPDATE. Told ya. Fake.