Shoot the switch to begin the hunt!
Now that you've got a Pack-A-Punched weapon, head to the West side of the map directly past the first set of doors from the start. Looking out past the barricaded window, you should see pillars in the distance. One of these pillars has a switch on it. Use your Pack-A-Punched weapon to shoot the switch. You should hear a distinct noise and a voice that wants to play 'Hide And Seek' with you. Oblige the voice and seek out the three toys he wants you to find.
The First Toy, located in an open furnace by the West teleporter.
The Second Toy, located on the catwalk of a building by the power switch.
The Third Toy, located in a chemical vat underwater by the East teleporter.
Once you've shot all of the toys, it's time to move on to the final step!