Black Hole :If A goes beyond the Event Horizon, B which is an observer will see A "slow down & freezes", why?

The photons emitted from 'A' will not get sucked into the black hole before 'A' actually crosses the event horizon. At some point near, but still outside of, the event horizon, it will take a million years for a photon to travel an inch in the direction of 'B', giving 'A' the appearance it has frozen there. 'B' might notice 'A' took 3 billion years to blink his eyes.