Police arrested a 20-year-old man in connection with a Molotov cocktail thrown at the home of OpenAI chief executive Sam Altman and an arson threat against the company’s San Francisco headquarters, CNBC reported on April 10 local time. There were no casualties. The charges against the arrested man have not yet been finalised.

San Francisco police responded at about 4 a.m. on Friday after receiving a report of a fire at Altman’s home in the North Beach neighbourhood. The suspect threw an "incendiary destructive device" toward the house, causing a fire on an exterior metal gate. He then fled on foot.

About 1 hour later, police responded again after receiving a report of a threat to set fire to an OpenAI office. Officers at the scene arrested the man, believing he was the same suspect who had earlier attacked Altman’s home.

OpenAI said no one was hurt and thanked San Francisco police for their swift response and city officials for their support. It also said the individual is in custody and it is cooperating with the investigation.

The incident occurred as controversy surrounding Altman and OpenAI continues. OpenAI faced criticism after signing a contract with the U.S. Department of Defense in February, and some activists left protest messages in chalk on the floors of OpenAI and Anthropic offices. Messages were also written in an OpenAI office urging employees to speak out against the contract.

OpenAI and Anthropic are competing for leadership in the large language model market. The combined private-market valuations of the two companies exceed $1 trillion, and the possibility of an initial public offering this year has also been raised. Both companies, however, continue to burn through billions of dollars in cash.

The incident shows that issues of executive and employee safety have come into focus as OpenAI continues its technology race and business expansion. The timing, as competition in the large language model market, controversy over the Department of Defense contract and a lawsuit with Musk overlap, also highlighted the level of tension surrounding OpenAI.