Outgoing Meta Chief Operating Officer Sheryl Sandberg has reportedly sold a fortune in company shares during her 14-year tenure at the social media giant formerly known as Facebook.

Sandberg, 52, was a fixture at Facebook over the last 14 years and played a key role in developing the advertising business that transformed the social media site into a revenue juggernaut over that period. She announced her resignation from Meta on Wednesday.

The company’s success also translated to a massive windfall for Sandberg – who has sold more than 75% of her after-tax shares in Meta through scheduled sale programs over the last decade, CNBC reported, citing calculations from analytics firm VerityData.

Sandberg has generated more than $1.7 billion through sales of more than 22 million shares, with her most recent transaction occurring in October 2019, according to the outlet. Some estimates place the executive’s windfall to be even higher.

“[Sandberg’s] sales over the past decade makes her one of the biggest insider sellers at any U.S. company,” Ben Silverman, director of research at VerityData, told CNBC regarding the transactions.

At present, Sandberg has an estimated personal fortune of $1.6 billion, according to Forbes. She ranks among the world’s richest female business leaders.

Of the 48 million shares, options and restricted stock units that she has amassed since joining Meta, some 20 million were sold for tax purposes, Sandberg’s spokesperson told CNBC. Another 22 million were sold through a 10b5-1 pre-schedule selling program.

The spokesperson added that Sandberg has gifted millions of additional shares toward charitable endeavors.

Sandberg still holds about 1.4 million Meta shares, according to Forbes. That stock was worth about $290 million as of Thursday and accounted for a less than 0.1% stake in the company.

Sandberg announced her surprise resignation from Meta earlier this week, citing a desire to focus on philanthropic initiatives and her upcoming marriage to marketing CEO Tom Bernthal.  

Meanwhile, Meta has reportedly initiated an internal investigation into Sandberg’s potential misallocation of corporate resources to help plan her wedding.

The Wall Street Journal reported that mounting internal scrutiny of Sandberg’s activities contributed to a feeling of burnout that factored into her exit from the company.