Haven't read the report, so all I can offer on the ancedotal cop freaked out story is... If after 15 shots, not one innocent bystander in a gym full of people was hit, I'd say it probably wasn't as outrageous as the story describes, but again, wasn't there.
I concur with YOUR personal decision to not get involved. The last thing I want in a volatile situation where a thug is armed with a gun is someone who isn't sure what to do, isn't aware of the risks, has no training or experience, to feel they have to do SOMETHING and then get someone, most likely themselves, seriously hurt or killed. Disgregard that statement if we are on a hijacked plane with terrorist, but for your "typical" robbery scenario, yeah, unless shots are being fired by the suspect, remain calm, make a note of clothing, description, distinguishing marks or tattoos for later. Be a good witness in other words.