(CNN) Scratch "build an underground lair" from your list of ways to elude Southern California's Fontana Police Department.

While serving a search warrant Thursday night at an alleged gang member's Fontana home, officers uncovered a manhole. When they opened it, they found a ladder under it, police said.

Down below was a cave with a secret shooting range and hideout. Inside, officers discovered a number of weapons and thousands of rounds of ammunition, "including a 100-round drum for an AR-15 rife," Fontana police said Friday on Facebook

The post featured a warning from the police, along with pictures of a sparse, unfinished underground space.

"We are the champions at Hide n Seek and no manhole will help you," it said.

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