I don't see why the police are different from the average joe in a few ways. Of course they have volunteered to uphold the law but, in My reasoning, most times they are responding to an after the fact situation and ALSO responding in force.(lotsa cops,lights and sirens)
Joe average on the otherhand, must deal directly with the situation,whatever that may be.
Understood the police do get into situations where the badguys are still there. So they are authorized superior firepower(and I don't deny that) while the average joe is limited and maybe outnumbered.