That one is not always there though.
Once you have 100 hidden packages it's always at the army base.
To get it, make sure you have 150 health (do the pizza missions to do this) and 150 armour (police missions). Fly in a helicopter from the north , land it quickly, and sprint to the hunter, take of and fly away in the same direction you came.
Alternatively, once you have done the mission "Cop Land" you get a police uniform at the Washington Beach police station. Put that on and you can walk into the army base without any body bothering you.