Another AU Concept
Role-switch ghost au
Basically, Tim went with Jay (and Brrian, disguised as hoodie, followed) to what would've been Jay's death. The confrontation with Alex occurs at the ledge where Brian would've died. During the confrontation, however, Tim ends up taking the bullet for Jay. He stumbles back, falling off the ledge. Both Brian and Jay witness this, and they each react differently.
Brian gets angry, attacking Alex with his crowbar, and, eventually, killing him.
Jay, however, rushes down to Tim, refusing to believe that he's dead.
This event leaves them both mentally scarred. Brian becomes a shut-in, and picks up a few hobbies along the way. Jay, quits his investigation, but still visits the place where Tim died at least once a week.
They both start seeing therapists.
Jay picks up a peculiar hobby. Ghost hunting. It help him cope, knowing that maybe he can reconnect with Tim.
Another note, Brian and Jay both get apartments, they live about a block apart.
So one day, Jay visits Brian. What happens is as follows:
Brian lets Jay in (Jay visits Brian three times a week to check up on him), and Jay is acting really nervous. Brian questions Jay's behavior, and Jay responds with "You'll never guess who I ran into."
At that moment, Tim phases in through the wall.
Brian is instantly confused, then attempts to hug Tim, but ends up nearly falling over.