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Sam Kirchner, a 27-year-old co-founder of the San Francisco activist group Stop AI, disappeared from contact around November 20–21, 2025. His disappearance followed an alleged assault on another organizer and warnings to police that he had discussed buying high-powered weapons and killing people at OpenAI. OpenAI subsequently locked down its San Francisco offices.
Those are reported allegations and precautionary actions—not proof that Kirchner owned a weapon, issued a verified direct threat, attacked OpenAI, or committed a crime. The San Francisco Standard reported that police had not corroborated the seriousness or nature of the alleged threats.
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What police reportedly warned
According to an internal San Francisco Police Department bulletin described by The San Francisco Standard, two callers familiar with Kirchner told police he had expressed a desire to buy “high-powered weapons” and use them to kill people at OpenAI. The bulletin identified OpenAI’s office at 1455 3rd Street as a possible first target.
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Why OpenAI closed its San Francisco offices
The Atlantic reported that OpenAI locked down its San Francisco offices on November 21 after receiving information that Kirchner had expressed interest in physically harming employees. WIRED also described the lockdown as a response to an alleged threat.
The available accounts do not establish that OpenAI received a verified direct threat, that Kirchner was near the building, or that an attack was imminent. The lockdown was a security precaution, not evidence that OpenAI was attacked.
What happened before Kirchner disappeared
The sequence below is based mainly on accounts from Stop AI members. Kirchner was not reached for comment in The Atlantic’s reporting, so the allegations do not have his recorded response.
- Planning dispute: Organizers disagreed about messaging for an upcoming demonstration.
- Argument over money: Members said Kirchner became angry and demanded access to Stop AI funds.
- Alleged assault: After the request was refused, he allegedly punched Stop AI leader Matthew “Yakko” Hall several times.
- Expulsion and police contact: Stop AI expelled him and contacted police.
- Disappearance: Associates later found his West Oakland apartment unlocked and empty. They said he had taken a bicycle and camping equipment but left his laptop and phone.
Stop AI members reportedly last had contact with him around November 20. On November 21, Kirchner posted that he was no longer part of the group.
Timeline of the reported events
| Date | What was reported | Important qualification |
|---|---|---|
| February 2025 | Kirchner and other activists were arrested during a protest involving an OpenAI entrance. | The Standard reported the arrest; the exact case outcome is not established here. |
| October 2025 | Stop AI promoted more confrontational demonstrations, including calls to close OpenAI. | Reported by The Atlantic. |
| October 28, 2025 | Hall was elected Stop AI’s leader, according to members quoted by The Atlantic. | Group members’ account. |
| November 16–17, 2025 | A planning dispute allegedly escalated; Kirchner allegedly punched Hall after seeking group funds. | Witness allegations; Kirchner was not reached for comment. |
| November 20, 2025 | Associates reportedly last contacted Kirchner. | Based on the group’s statement as reported by the Standard. |
| November 21, 2025 | He missed a court hearing, police received warnings, and OpenAI locked down its San Francisco offices. | The key date in the incident. |
| December 2, 2025 | The Standard reported that police were still searching for him. | It did not establish his later whereabouts or final legal status. |
| December 4–5, 2025 | The Atlantic published its feature; Futurism published the headline that prompted broader coverage. | These were developing-event reports, not a completed criminal investigation. |
Who Sam Kirchner is
Kirchner moved from Seattle to San Francisco in 2024. The Standard and his LinkedIn profile described earlier work as a mechanical engineering technician and DoorDash delivery driver. He co-founded Stop AI and publicly argued that superhuman artificial intelligence could cause human extinction.
He also had an earlier legal matter. The Standard reported that he was arrested after a February protest at an OpenAI headquarters in which activists allegedly barricaded doors. He failed to appear at a November 21 hearing, and a judge issued a bench warrant. A bench warrant is not a conviction, and the available material does not establish the charges’ final disposition.
What Stop AI believes—and what “anti-AI” leaves out
Stop AI says it wants a permanent global ban on developing artificial superintelligence. Its activities included demonstrations, leafleting, public messaging, T-shirt events and civil-disobedience tactics. Members described the group as committed to nonviolence, while also acknowledging a more confrontational approach than some other AI-skeptic organizations. Its stated mission is available at stopai.info.
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“Anti-AI” is an imprecise label. The broader movement includes people concerned about:
- Artificial general intelligence and superintelligence;
- Job displacement and economic concentration;
- Energy use and environmental costs;
- Copyright and creative-property disputes;
- AI-enabled surveillance and military applications; and
- Lack of democratic control over frontier-model development.
Those concerns do not imply support for violence, and Kirchner’s alleged conduct cannot fairly be treated as representative of every AI critic.
Stop AI and PauseAI were not the same organization
The Atlantic described a divide between Stop AI and PauseAI. Stop AI favored more confrontational demonstrations and opposition to further progress toward superhuman AI. PauseAI advocated a pause until advanced systems could be developed safely and under democratic control, while disavowing illegal or disruptive tactics.
The disagreement was also about rhetoric. Some activists used stark extinction warnings; others argued that presenting human extinction as nearly certain and imminent could alienate the public, intensify fear or make violence appear morally justified. That is a debate about possible effects of rhetoric, not evidence that rhetoric caused the alleged assault or weapons claims.
What Stop AI members said after the disappearance
Members disavowed the alleged assault and any possible violence and said the organization remained committed to nonviolence. Some said they were more worried about Kirchner’s safety and mental state than about a broad public danger. Organizers said they did not know of a specific direct threat from him, while also warning that he might be a danger to himself or others.
Friends speculated that he could be camping or experiencing a mental-health crisis. Those possibilities were not verified, and there is no basis here to diagnose him.
What remains unknown
- Kirchner’s location after the early-December 2025 reports;
- Whether he possessed a weapon;
- Whether he intended to attack OpenAI or anyone else;
- Whether prosecutors filed charges over the alleged weapons statements or assault;
- The final status of his bench warrant and earlier protest case; and
- Whether he was later found, arrested, hospitalized or cleared.
The cited reporting provides a December 2025 snapshot. It does not supply a verified final resolution as of the material available for this article.
Why this episode should not be generalized
The incident combines a missing-person report, an alleged interpersonal assault, an uncorroborated weapons warning and a corporate lockdown. Treating those elements as established criminal conduct would go beyond the evidence. So would describing Stop AI—or the wider AI-safety and AI-opposition movements—as violent based on one expelled member’s alleged actions.
The responsible conclusion is narrower: police took warnings seriously enough to alert personnel and OpenAI took precautionary security measures, but the available reporting does not prove that Kirchner bought weapons, made a verified murder threat or attacked OpenAI.
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