UH OH VAMPIRE WARNING AHEAD
From the shadows, Aziraphale keenly watched the concert, not knowing what to make of it. He recognizes many of the party-goers... vampires, werewolves, even hunters... but to watch them gathered together is confusing to say the least. He expects a fight to break out at any moment, and frankly is disappointed when it does not happen... a blood bath between the three groups would be amusing.
Like the predictor that he is, Aziraphale spots the human pulling away from the crowd, cheerful, unarmed, oblivious to danger... a perfect target. He watches carefully as Baymax moves further and further away, timing it just right to make his move. And when he does, he pounces.