Brian G. Castillo, 20, of Round Lake Beach.

Police arrested a man after finding him in possession of a loaded ghost gun and a small amount of drugs while responding to a house party complaint in Grayslake, prosecutors said.

Brian G. Castillo, 20, of the 1500 block of Vine Avenue in Round Lake Beach, was charged with aggravated unlawful use of a weapon, defacing firearm identification marks and attempted possession of a controlled substance.

Lake County Assistant State’s Attorney Mary Daly said the Grayslake Police Department responded Sunday to a call of a noise complaint.

Officers arrived to find a house party and partygoers scattering.

Officers found Castillo, who was trying to crawl out of a back window, Daly said.

They shined their flashlights onto Castillo and told him to stand up.

Castillo complied and turned around, at which time officers saw the butt of a handgun in his waistband.

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Officers instructed Castillo to put his hands up as they removed the gun from his waistband.

Daly said the gun was determined to be a Polymer80 9mm ghost gun, which replicated a Glock 19. The gun was loaded.

While booking Castillo after his arrest, they found a small baggy of suspected cocaine and a dollar bill. Both tested positive for cocaine, Daly said.

Lake County Judge Chris Morozin ordered Castillo held on a $40,000 bond.

Castillo was released from the Lake County Jail the same day he was transported to the jail.

A status of attorney hearing is scheduled for November 20.