If his account is accurate, there were dozens of people jammed into a narrow, fenced in alley outside that door, trying to escape through a small opening in the fence. As cruel as holding the door closed sounds after the fact, there could have been deaths in the alley as well due to people being crushed to death. It may have been a reasonable response given the circumstance.
Having been almost crushed to death and pushed through a glass security door at a UFO concert I will reserve judgement.