I agree in this situation ( of which we have the benefit of hindsight) that would have likely worked. But from her perspective in that position; Considering all the possible scenarios with her son a pair of scissors and two cops, how many of those possible scenarios would her son be shot and killed? Many I think.

I can't fault her for trying. Neither can I find fault in the Police for shooting a crazy Mexican kid with scissors.

What we seem to be missing here is a big dad to subdue the son.

The mother was to weak. And little brother was not experienced enough to be of more help.