matthew56, mahalo for the quick and thoughtful responses. I understand and partially agree with your 2nd and 3rd points. In the 1st, though, you seem to be agreeing with me, that having a gun didn't protect the officer from harm. From what I see, you haven't answered my second question: "If the attacker, Ftouhi, had had a gun, how many more would he have harmed or killed?" The answer, IMO, is that he could've killed many more, depending on the type of weapon and his skills. 

I admit that if some of the people around Ftouhi were carrying, they could have fired back and wounded or killed him, but in the time that it takes for them to react, the attacker would have still caused a lot of damage. 

And there's always the problem of collateral damage when more than one person is firing from different directions. Compound that with a wide range of skill levels and the confusion LEOs face in distinguishing the good guys from the bad, and we have the kind of chaos that leads to bloodbaths.