"Hostage taker" is lucky someone didn't lay a smackdown on him.  
I've been in this type of event, both as a bad guy and as a good guy.  Much more fun to be a baddy TBH.  We were all on the same sheet of music, surrounding people were warned and/or recruited for roles.  Even then, we had "umpires" in full uniform stationed around to tell people what went on.
Still there are failures.  Most notably, a police officer shot two soldiers going through SF training, not knowing they were playacting, and they didn't know he wasn't playacting.  A tragedy which caused several lawsuits and many rules and procedures being changed.
The best laid plans...  and it's even worse when you plan and don't tell anyone.