[nascarnation]

This is just a guess.

How about threading a length of small diameter stiff wire (like the safety wire for aircraft fasteners) through any gap between the door and jamb near the latch and popping the latch?

These obviously aren’t dead bolted since it’s a safety issue, just a spring latch keeping it in place if you pull from the outside.

[no-to-illegals]

Your answer is a maybe. Not doubting this is possible. Would explain the door being opened by the perp, if was possible. A wire could be used.

[cherry]

a caller on one of the tv stations said the guy was in the theatre and took a cell phone call, but instead of going to the lobby, he went out the exit door....I surmiss he put something in the door to get back in....

[fatima]

They said he answered his phone and left by that exit.He must of jammed it.His car was parked right outside the exit.He put his gear on and went back in.He had to have practiced that.