Palo Alto Online: 'Astronomical' Rise in Ghost Guns has Law Enforcement Worried

A joint operation led by the San Mateo County Sheriff's Office ended last week with the seizure of 30 illegally held firearms and the arrest of four men, believed to have trafficked the weapons from Arizona and sold them throughout the county.

The massive, monthslong investigation by the Bureau of Alcohol, Tobacco, Firearms, and Explosives (ATF), the San Francisco Police Department and the San Francisco Drug Enforcement Administration Metro Task Force is the latest crackdown on the growing market for illegal firearms.