Okay but it 100% was Arthur Leigh Allen tho. I've done days of research: binging all of mindhunter, watching the buzzfeed unsolved videos, and now this? As a certified detective at this point, I'm confirming once and for all it was Allen.

Case closed.

EDIT: I'm embarrassed to admit this, but Zodiac scared me so much I fr checked under my bed before I went to sleep. Idk what came over me but I couldn't get the thought out of my head that he was there until I physically got up and checked. God damn you Fincher.