"OK, how about a suspect of the same description, driving the same make and model car, but a CANADIAN citizen suspected of murdering his family and possibly fleeing TO the US?"
Not a US citizen ? No Problem, you are already checking them out - if one fits the perp, hold him until the Canucks come and clear him.
I would expect the same if I fit the description of someone another country I visit were looking for.
OK, OK, I give up.