Warren Buffett just gifted $759 million of Berkshire Hathaway stock to good causes — after donating $4 billion in June

• Warren Buffett made a surprise donation of $759 million in stock on Wednesday.

• The investor split a total of 2.4 million Class B shares between four of his family's foundations.

• Buffett has gifted 52% of his Berkshire Hathaway shares since 2006, but still holds a 15.5% stake.

Warren Buffett must be feeling grateful this Thanksgiving, as he unexpectedly donated $759 million to good causes on Wednesday.

The famed investor and Berkshire Hathaway CEO converted 1,600 Class A shares in his company into 2.4 million Class B shares, then gifted all of them to four of his family's foundations, SEC filings show.

Buffett gave 1.5 million shares, worth $474 million as of Wednesday's close, to the Susan Thompson Buffett Foundation, named after his late wife.

He also gifted 300,000 shares, valued at $94 million, to each of his three children's foundations: The Sherwood Foundation, the Howard G. Buffett Foundation, and the NoVo Foundation.

Buffett told CNBC that he made the donations to thank his children for their charitable work.