On PCP or armed or not..... first thing I'd do is leave him alone and mind my own business if he hasn't yet caused any harm or broken any laws that I have evidence for. It is certainly NOT acceptable to just assume every citizen who happens by your road block is on PCP and armed then proceed to treat them as if you know they're guilty of something and you just need a few moments of conversation to determine what it might be they can be arrested for.
So step 1 is respect the rights of the citizens you work for and serve. Step 2 is repeat step 1 and if you can not accept the fact that you do work for the citizens or the fact that the citizens do have rights which you have no authority over, then you really ought not to be in the law enforcement profession.
How's that strategy going with Iran????