San Carlos home search uncovers ghost guns, suspected fentanyl and a much bigger case than detectives expected
San Mateo County, California – What started as a separate criminal investigation in San Mateo County led detectives to a San Carlos home where authorities say they discovered homemade firearms, suspected fentanyl and materials used to package drugs.
The discovery resulted in the arrest of a 52-year-old man who investigators believe was manufacturing firearms inside his residence, despite having no guns legally registered in his name.
Last week, the San Mateo County Sheriff’s Office announced the arrest of Joshua A. Harris of San Carlos following an investigation conducted by its Crime Suppression Unit. Detectives recovered three unregistered firearms without serial numbers, commonly known as “ghost guns,” along with approximately 12 grams of suspected fentanyl and numerous firearm components.
According to the Sheriff’s Office, the investigation took a significant step forward on October 19, 2026, when detectives obtained a judge-approved search warrant for a residence in the 1700 block of Alameda De La Pulgas.
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The warrant was connected to an earlier, separate investigation that eventually brought detectives to the property.
Four days later, on October 23, investigators carried out the search. Before entering the home, authorities conducted a nearby traffic stop and took Harris into custody without incident.
What detectives subsequently found inside the residence raised concerns about both illegal firearms and narcotics.
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Among the items recovered were three firearms that had neither registration records nor serial numbers. One of them was identified as an AR-15. Investigators also discovered numerous gun parts, suspected fentanyl and drug packaging materials.
Authorities believe Harris had been manufacturing firearms at the property. The Sheriff’s Office also confirmed that Harris had no firearms legally registered to him.
Ghost guns are particularly difficult to trace because they lack the serial numbers typically used to identify firearms during criminal investigations. Their presence, combined with the suspected narcotics and additional gun components, became a central part of the case against Harris.
Following his arrest, Harris was booked into the Maguire Correctional Facility on multiple felony allegations involving firearms, controlled substances and the illegal manufacture of a destructive device.
The listed charges include transporting or selling controlled substances, including a charge involving transportation between counties, possessing a controlled substance while armed with a loaded firearm, illegally possessing an assault weapon and possessing a firearm without a serial number.
Harris also faces an allegation of manufacturing a destructive device without a permit. The Sheriff’s Office did not provide further details about that particular charge in the information released.
The investigation highlights how a case that initially began elsewhere can lead authorities to additional suspected criminal activity. In this instance, detectives ultimately recovered three unserialized firearms and suspected fentanyl from a single San Carlos residence.
The Sheriff’s Office is asking anyone with additional information about the investigation to contact detectives at 650-363-4911.
People who wish to remain anonymous can submit tips by calling 1-800-547-2700.
The allegations against Harris remain criminal charges, and he is presumed innocent unless proven guilty in court.
