Nothing like inventory control.
Fire the facility manager.
I think the perp was the facility manager. The facility's job was to shread the firearms. What a perfect place to make off with some guns. Go look through the pile of shredded steel and plastic and prove that it's one or two guns light.
From the article:
Yates admitted to stealing at least 3,000 slides, a key part of a gun allowing it to fire, from Glock semiautomatic handguns.
What a great scheme. Take the slides (presumably with barrel and recoil spring, striker, and extractor) and shred the serialized frame.
Then sell the slide and barrel on Gun Broker to people building their own Glocks from unfinished 80% lowers.