(KRON) -- A suspected internet child predator was both arrested and booked into county jail on Thursday, the Marin County Sheriff's Office said. During "Operation: Catch Them All," a four-day undercover sting operation to catch internet child predators, a detective from the Roseville Police Department reached out to MCSO detectives regarding a suspect from this operation based out of unincorporated Mill Valley. "Roseville PD detectives requested assistance verifying the suspect living at the house they believed he lived in and with serving the arrest warrants," the sheriff's office said. On Thursday morning, sheriff officials said RPD detectives arrested the suspect "while he was leaving for work." Once he was arrested, MCSO detectives executed a search warrant at the suspect's residence. During the search, sheriff officials found 11 unregistered firearms and ammunition pictured below. MCSO said one of the firearms seized was an un-serialized AR-15 that had been manufactured from an 80% lower receiver.  AR-15 Lower Receivers are items that have not yet reached a stage of manufacture to be considered a firearm. (example pictured below) Close-up of the handle, upper and lower receivers, and trigger of an Essential Arms Company Essential Arms J-15 semi-automatic rifle, seen against a white background, New York, New York, March 21, 1994. The photo was taken as part of a shoot for Newsweek magazine. (Photo by Michel Delsol/Getty Images) The suspect, who was not named, was convicted of a felony in 2019 and is prohibited from possessing firearms and ammunition, the sheriff's office said. According to MCSO, he was booked into Marin County Jail for the following: Felon in possession of a firearm Felon in possession of ammunition Possession of an unregistered assault weapon Possession of an un-serialized firearm The suspect, according to sheriff officials, faces a half-a-million-dollar bail. The Marin County charges add an additional bail of $50,000, MCSO said.