Suchir Balaji, a former OpenAI engineer and whistleblower who helped train the artificial intelligence systems behind ChatGPT and later said he believed those practices violated copyright law, has been found dead in an apartment in San Francisco, authorities said.

The body of Suchir Balaji, 26, was discovered on 26 November after police said they received a call asking officers to check on his wellbeing.

The San Francisco medical examiner’s office determined his death to be suicide, and police found no evidence of foul play.

Balaji who until recently worked at OpenAI but became a vocal critic of OpenAI’s practices, which has been fighting a number of lawsuits relating to its data-gathering practices.

His parents Poornima Ramarao and Balaji Ramamurthy said they are still seeking answers, describing their son as a “happy, smart and brave young man” who loved to hike and recently returned from a trip with friends.

Balaji grew up in the San Francisco Bay Area and first arrived at the fledgling AI research lab for a 2018 summer internship while studying computer science at the University of California, Berkeley. He returned a few years later to work at OpenAI, where one of his first projects, called WebGPT, helped pave the way for ChatGPT.

Balaji began questioning his work and his organisation’s work writings online and other media used to train GPT-4, the fourth generation of OpenAI’s flagship large language model and a basis for the company’s famous chatbot, especially after newspapers, novelists and others began suing OpenAI and other AI companies for copyright infringement.

US and Canadian news publishers, including the New York Times, and a group of best-selling writers, including John Grisham, have filed lawsuits claiming the company was illegally using news articles to train its software.