So I was just being curious and I found out who the movie and book the exorcist is based on, His name is Ronald Hunkeler. He is a retired NASA Rocket Scientist.
His 1954 Senior Year book photo. This was five years after the exorcism
Green X is him, I think this was taken the year before or the same year as the exorcism.
Father William Bowden, who performed the exorcism.
The house Ronald lived in when the events occurred.
What someone claims is a picture of him today.