Does Hallow remove the listed conditions when cast?

The spell Hallow has this effect when cast:

First, celestials, elementals, fey, fiends, and undead can’t enter the area, nor can such creatures charm, frighten, or possess creatures within it. Any creature charmed, frightened, or possessed by such a creature is no longer charmed, frightened, or possessed upon entering the area. You can exclude one or more of those types of creatures from this effect.

If a creature within the target area is charmed, frightened, or possessed by a listed creature type when the spell is cast, is that condition ended, suspended, or unchanged when the spell is cast?

In other words, is casting this spell on the area such a creature is in enough to end one of these effects, or must the caster get them to go in and out of the spell’s area too to achieve this?