again you have the luxury of hindsite,they have to make that decision in a split second.and his past does matter,sorry your wrong.
Not looking at hindsight at all.  Here's a couple of possible assumptions you are running under:
-  The police officers were aware of the man's meth history
-  The police officers knew of him making threats with a gun
Here's what we do know:
-  A man threw a rock or rocks at 3 police officers
-  They chased him and shot him
-  The man was not a threat without a rock in his hand
-  Its debatable that he was a deadly threat with a rock in hand
-  The police had the reasonable means to subdue him
This is wrongful death, plain and simple