Google co-founder Sergey Brin gifted Alphabet Inc. shares worth roughly $600 million on Thursday during a week that saw his wealth grow by the most in over two years.

The gift, disclosed in a filing Monday, doesn’t specify who received the 5.2 million shares, which were evenly split between newly converted Class A stock and Class C stock. They could be directed to charity, or given to other financial vehicles or trusts.

Google didn’t respond to a request for comment on the filing.

Brin and co-founder Larry Page saw their wealth surge by a combined $18 billion last week, their biggest gain since February 2021, after investor frenzy around artificial intelligence boosted Alphabet’s stock. The day before his share gift, the Mountain View, California-based company announced a more conversational search engine and said it was making its AI-powered chatbot more broadly available.

Brin’s net worth is now $100.7 billion, according to the Bloomberg Billionaires Index. His fortune, the ninth-highest in the world, is largely made up of a combination of Class B and Class C shares of Alphabet. He’s sold more than $10 billion worth of shares since the company’s initial public offering in 2004, according to data compiled by Bloomberg.

The stock gift follows a similar move by Brin late last year, when he transferred about 1 million shares. He also used some of his Alphabet stock to set up a new nonprofit called Catalyst4 focused on health and climate change, though filings show the majority of its funding so far comes from Tesla Inc. shares sold near their peak in late 2021.

--With assistance from Tom Maloney.