To find the Security’s Cooler Key for the Security Guard’s Cooler in Dead Island 2, head to Action Alley during/after the Michael Anders and the Holy Grail story quest.
Once at the spot shown in the map above, take out the Monarch Security zombie then loot the Security’s Cooler Key from where he falls. With the key in your inventory, head on over to the security booth to find the Security Guard’s Cooler.
Use the key to open the cooler. As a reward, you’ll find the Damaging Police Battalion. For more guides on Dead Island 2, click here!