Your instincts about someone new on the scene are correct. But stay quiet for now.
In Detail
Your instincts about someone who is new on the scene are right on target, but that doesn't mean you should advertise your opinions to the world at large. Keep this information under your hat for now, or for at least as long as it takes you to get the evidence to back your instincts up. But you might not need to wait -- this person is awfully cocky and careless, and could soon reveal his or her true colors (to the great surprise of many people).