Jay has lived alone for more than a couple of years, mostly because of the roommate he had shared the place with hadn't came back home yet. He honestly didn't know when the roommate was coming back, but he at least was still able to keep in contact. That said roommate was you, and you were coming back to the apartment today without Jay's acknowledgement to surprise him. When you came back you were introduced to yelling coming from Jay's room, which was probably him just recording another video