It occurs to Father Burke that he can enter the castle through the delivery entrance. Just before he hears the bell, he looks at the delivery door. As the camera pans from him to the door, there is a boy standing beside him who turns to look at Father Burke.
I assume this is an editing error since the only boy in the story is a possesed child from his past and he'd been fighting him in earlier scenes. The boy in THIS moment is completely passive and his presence doesn't make sense. If he is the possessed boy, why is he suddenly there for a split second in a passive manner? If he isn't that boy, where did he come from? I feel like there must be a deleted scene and this moment is a remnant.