[stlnative]

THIS IS HOW I TAKE IT...

The sniper has left a number, probably a pay phone number that is located somewhere. The police now have taken over that number and the are asking the sniper to call them at that number. The cops do not have to hang around at the pay phone they can disconnect the phone number at the pay phone and assign it to a phone at the police station etc... Even though this does not make sense and why would he not call the 1-888 number? Maybe he thinks the cops will actually hang around the pay phone that had the number assigned to it.

[stlnative]

OR MAYBE...

The sniper left a note and asked them to put a certain phone number into service (maybe a phone number the sniper will easily remember or the phone number spells something out). The cops have now put the number into service and it is working as a direct link to maybe Chief Moose. They are letting the sniper know that his request has been done and it completed. Now they want him to call.