Since the explosive forces, swirling gasses, and gravitational rotations create a total force that is NOT spherical, there is likely a window of time when part of your blackhole requires an FTL escape velocity while the other hemisphere still lets loose photons and gamma rays. So a critical atom (singular)? No, probably not. There is also an accretion disc around blackholes which block and reflect light back into the central mass. So for a non-zero amount of time, the blackhole is not trapping photons but the blackhole system (the Greater Metropolitan Blackhole) does effectively trap everything.

Tl;dr there would be a window of time and mass during which your escape velocity is sub c but nothing escapes AND/OR your escape velocity reaches c but not uniformly in a sphere.