Once Henry gets upstairs and pulls the switch there, the room goes dark and the Projectionist vanishes. As Henry climbs the stairs out of the Maintenance department, the Projectionist reappears and chases Henry one last time.

Why did bendy save you from the projectionist?

He made sure of his progress by visiting him in the vents, but when the Projectionist but about to kill Henry, Bendy stepped in and killed the Projectionist. He was only protecting Henry temporarily, at least, until he managed to find Alice. This is why I think Bendy saved him.

Why does bendy kill Henry?

He also attempts to kill Henry due to the fact that he knows that Henry intends to destroy him using the "The End" Reel. Also, his transformation into Beast Bendy might have clouded his thoughts, and make him just hurt anything he sees.