Even though they say he had cameras in & outside of his room, they say they were NOT recording! I do not trust them.
I read the police said Stephen had a signal jammer to block the hallway cameras. That way he or whoever else he was working with could slip into that stairwell unnoticed and blend in with the Carnage to escape. I don’t remember what movie it was but I distinctly remember a scene where the criminal dresses as a firefighter with a mask on to blend in and escape from the crime scene.