  We study the final fate of a very massive star by performing full general
relativistic (GR), three-dimensional (3D) simulation with three-flavor
multi-energy neutrino transport. Utilizing a 70 solar mass zero metallicity
progenitor, we self-consistently follow the radiation-hydrodynamics from the
onset of gravitational core-collapse until the second collapse of the
proto-neutron star (PNS), leading to black hole (BH) formation. Our results
show that the BH formation occurs at a post-bounce time of ~300 ms for the 70
Msun star. This is significantly earlier than those in the literature where
lower mass progenitors were employed. At a few ~10 ms before BH formation, we
find that the stalled bounce shock is revived by intense neutrino heating from
the very hot PNS, which is aided by violent convection behind the shock. In the
context of 3D-GR core-collapse modeling with multi-energy neutrino transport,
our numerical results present the first evidence to validate a fallback BH
formation scenario of the 70 Msun star.
