Right on. You shoot a Big Bang Attack into the building where he landed. Kaboom!!! The blasts lands and creates a spherical orb of energy that would make Goku impressed. Unfortunately, Majin Buu was waiting for you to do just that. He is already on a collision flight path with you now. He rams your back and sends you hurtling into your own blast. He then shoots a quality beam of his own, making your energy orb explode along with you in it.