I did a little snooping, and found that he had bought from
tacticalgearnow:
It appears that he purchased $306.79 worth of merchandise. They did NOT sell him a vest or a helmet. Looking at their website, you have to have some sort of LEO/Mil ID to purchase.
What the Chief of police says is that the guy had a ballistic tactical vest, ballistic helmet, throat and groin protector. No mention of bicep/shoulder protection.There is a description of some sort of leggings. Whether they are ballistic or not is anyone's guess.
So, something like this, but in black:

Because I am making the huge logical leap that the chief of police would not say "ballistic tactical vest" unless he meant a ballistic tactical vest, the scenario is bad.
I used to wear that stuff when I ran with Dallas SWAT.
You are pretty protected. Forget about pelvic girdle shots incapacitating.
It's a bad scenario. Honestly, you would be best fighting your way to an exit, shooting to keep the guy distracted. But, I honestly do not know if I would have picked up on the body armor in a dark theater with bullets incoming. I still say your best bet would be to get cover/concealment, try to flank and engage.
It is a crap situation. There is no neat tactical maneuver which would give you the upper hand. You have to just fight your way to victory, or die trying.