My personal view is that Carol Ann spoke to her attacker in the church and discussed she was off the the library and the church was a spur of the moment idea.
The attacker realised that nobody was aware that Carol Ann could be connected to the premises and slid the bolt on the door and went about his attack. I don't think Carol Ann was dragged up the loft stairs until after she was dead or unconscious. I know the limited info we have suggests it was before the attack that she was dragged, feet first, up the stairs. I disagree ,if she wasn't able to remove the sock in her mouth to scream, whilst her legs are held, IMO, therefore she's incapable.
The attack took place with the intention of the body being hidden until such time it could be removed (notice the back of the church on Google, path through cemetry to parking lot at rear of Rectory house) So, when the girls and bank clerk come knocking the perp looks out the window to check if it's flock or staff trying to get in. That's when to his horror he notices the bike and realises he can't just open the door and allow the flock to enter. So, he waits and makes his getaway at the rear of the church after unlocking the door. If it wasn't for that damned bike I don't think Carol Ann would have been found near the church, if found at all.
All my opinion from the scanty facts we know.