A California police department discovered a secret underground shooting range belonging to a "known gang member", complete with numerous weapons and ammo.

The Fontana Police Department discovered a secret shooting range and hideaway at a gang member's home. (Fontana Police Department )

The Fontana Police Department posted pictures of the secret hideaway that they found Thursday night.

Police said officers from the gang unit were serving a search warrant at the residence when they came across a manhole that led to the hideaway. The area also contained thousands of rounds of ammunition and weapons including a “100 round drum for an AR-15 rifle.” The evidence was confiscated and multiple suspects were booked, police said. Police did not say how many suspects were taken into custody or specify the gang.

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In a press statement, police had a warning for those who wanted to be a gang member, while offering some advice.

The Fontana Police Department posted pictures of a secret hideaway and shooting range they discovered at the residence of a “known gang member” on Thursday night. (Fontana Police Department )

“We will never give up on keeping our community safe and free of violence,” the press statement read. “We are the champions at Hide n Seek and no manhole will help you. If you hide we will find you. If you run you will go to jail tired. If you do crime in our city, we will hunt you in the pursuit of justice for our community.”

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Police also suggested the gang members “put as much effort as you did in your underground cave, into becoming a productive member of society.”

“You will thank us later for this advice,” police said.