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.
The Professional. Been done many times in many movies with various first responders.
Sorry. In The Professional I think he went out as a SWAT guy.