Waymo Detects Loaded Ghost Gun Inside Robotaxi, Two San Francisco Minors Arrested

The Stop

Just before 4 a.m. on September 3, a Waymo robotaxi pulled itself over on the 800 block of 40th Avenue in San Francisco's Richmond District. The company said it had detected a "violation of our terms of service involving a firearm" inside the car, according to a Waymo spokesperson who confirmed the incident to the Los Angeles Times. Waymo alerted emergency services and says it "cooperated fully" with San Francisco police.

Officers responded and conducted what SFPD spokesperson Allison Maxie called a "high-risk vehicle stop," according to SFGATE. They detained two juvenile passengers, a boy and a girl. A search of the car turned up a loaded, AR-style assault rifle that police described as a ghost gun, an unserialized weapon that's difficult to trace back to a manufacturer or owner. Officers also found suspected marijuana and mace spray on the teens.

Both were arrested on charges related to illegal firearm possession and booked into San Francisco's Juvenile Justice Center. Police have not released their names because they're minors. SFPD says the investigation remains open and active.

How the Car Knew

Waymo's exact detection method remains unclear. Hoodline reported that Waymo's vehicles rely on interior cameras and remote human monitors who can disable a trip or contact authorities, citing the company's rider terms.

Privacy advocates have raised questions about what it means for a private company to watch and record riders inside a car they paid to ride in, and decide on its own when to alert police. Waymo has not detailed its interior monitoring policies publicly beyond what's in its terms of service.

In this specific case, the monitoring caught two minors carrying a loaded, untraceable rifle at 4 a.m. The system flagged the weapon and alerted authorities.

Not the First Time

This is the second time in two months Waymo has flagged juvenile passengers to police. In July, the company alerted San Mateo police after remote monitors saw two 15-year-old boys drinking alcohol and firing what turned out to be Orbeez water beads out the windows of a Waymo, according to CBS News reporting cited by Hoodline. In that case, San Mateo police spokesperson Jeanine Luna said the teens were told the vehicle "had issues" rather than being informed police had been called, though the doors remained unlocked the entire time.

It's not clear from available reporting whether Waymo used a similar cover story with the two teens carrying the ghost gun on September 3.

A Policy Question Nobody's Answering

Waymo's rider rules generally require passengers to be at least 18 unless accompanied by an adult in most California markets, according to Hoodline's review of the company's terms of service. Two unaccompanied minors, one with a loaded rifle, were in the back seat anyway. Neither Waymo nor SFPD has explained how the ride was booked or whether the company's age-verification process has any teeth beyond a checkbox at signup.

The Ghost Gun Backdrop

California Department of Justice data show law enforcement recoveries of untraceable ghost guns statewide jumped from 11 in 2014 to more than 10,000 in both 2021 and 2022, according to figures reported by Hoodline. State lawmakers passed Assembly Bill 1621 in 2022 specifically to crack down on unserialized firearms. Four years later, teenagers are still getting their hands on them, and California courts are still processing new cases, including a March 2025 arrest of two male juveniles near the Stonestown Galleria after a foot chase turned up a ghost gun and an AR-style replica, per the same Hoodline account.

California has some of the strictest gun laws in the country. A homemade, untraceable rifle ended up loaded in the back of a robotaxi with two minors inside. Whatever AB 1621 was supposed to fix, it isn't stopping supply from reaching teenagers.

What's Unresolved

SFPD says the case is open and active, meaning charges against the two juveniles haven't been finalized in public records. Waymo hasn't said how its detection system identified the firearm, whether it was visual, audio, or otherwise, nor has it explained how two minors got into an autonomous vehicle alone despite its stated age policy. Those are the two open threads: what tripped the alert, and how the ride got booked in the first place.