If the guy is used to phoning in saying he is the sniper and being put on hold or switched around incompetently…then they should use that. Get their butts organized, but still pretend to be incompetent and in disarray. Then when anyone calls claiming to be the sniper, immediately start tracing the call…but give him the impression you are an incompetent phone receptionist and put him on hold and not believe him when he says he is the sniper…
The police could even claim the phone number he is using somehow got out and the line is being flooded with calls of people claiming to be the sniper…
It will frustrate and piss him off…but that will make him screw up.
Phone traces don’t work in real life the same way they do in the movies… there’s no countdown timer until the trace is finished, no magic number of seconds when the sniper could say “Ha! Too late!” and hang up to avoid being traced.
And under normal circumstances, you can trace back the originating phone of a call regardless of the length of the call, or even equipment on your end (Just call up the phone company and ask for the source of any incoming calls in a certain time frame).