It was Carl.
Blatty said it was and the clue is he makes the Catholic cross sign on himself at one point. Think it was in the book and not the movie but can’t remember at the moment.
I believe it could have been Burke Dennings, was he aware of Regan’s condition, and could he be guilty of a bit of mischief, to get a reaction, and possibly the reaction was that he was firstly murdered and then pushed from the window.
It was Carl. I did a video on it. I even brought up the brief shot of “the shoe and the hand” seen at the floor during the crucifix masturbation sequence.
Was Chris angry about it? She acts so in the movie, how she questions everyone. I know she’s an atheist, but might it have helped? Or did it make things worse? Or was she upset that those close to her would be trying impose their beliefs on her daughter? I always assumed that was the reason for her snippy tone, but she spends half the movie screaming, wiggingbout and snapping at everyone around her. Mind you, if my pre-teen was upstairs doing/saying half the stuff Regan was, I’d be a little tense and snappy too!