Ghost attacks teen on stairwell

This video looks a little suspicious and could easily be fake but I thought I would share it anyway.

It shows two teens walking down a stairwell only to be confronted by a ghostly shadow figure which then proceeds to attack one of the teens.  His friend tries to drag him away from the attack.

The shadow figure seems to also have some kind of weapon which it uses in the attack on the boy.

As soon as the two teens run back up the stairs the ghost seems to vanish.

Real or fake?  what do you think?