Tony Hsieh, the former CEO of Zappos.com who pioneered internet advertising and revolutionized the shoe business, died on Friday aged 46. He was with family at the time.

Hsieh had retired from Zappos, the iconic online shoe retailer, earlier this year after 21 years. He'd also been a key figure in revitalizing downtown Las Vegas, as well as an inspiration to other entrepreneurs.

"It is with very heavy hearts that we are sharing some very sad news with all of you, as we have learned that Tony passed away earlier today," Zappos CEO Kedar Deshpande said in a letter posted to the company's website.

"Though Tony retired this past summer, we know what a tremendous impact he has had on both Zappos and on Zapponians, as he has dedicated the past 20 years focusing on the success of both the company and our employees."

His cause of death has not been announced.

Hsieh is widely regarded as the man who brought advertising to the internet through advertising network LinkExchange, which he co-founded in 1996.

Microsoft purchased LinkExchange for $265 million in 1998 when Hsieh was just 24 years old. He went on to invest $500,000 in ShoeSite.com in 1999, an idea conceived by a younger entrepreneur, Nick Swinmurn.

The name was soon changed to Zappos and it became a pioneer of ecommerce. The company was sold to Amazon in 2009 for 10 million shares of stock, which Hsieh said were worth $1.2 billion at the time.

As CEO of Zappos, Hsieh was famous for his emphasis on customer service and the company was widely praised for its treatment of employees. Hsieh also wrote a New York Times best-selling book Delivering Happiness: A Path to Profits, Passion, and Purpose.

"A lot of our growth and innovation moving forward will be based on thinking about what we're in the business of differently," Hsieh told Footwear News last year. "We used to say we're a service company that just happens to sell shoes, and now it's turned into: We're a service company that just happens to sell blank."

Hsieh later focused on revitalizing parts of Las Vegas, where Zappos was based. Nevada Governor Steve Sisolak offered his condolences overnight and praised Hsieh's work in the state.

"Tony Hsieh played a pivotal role in helping transform Downtown Las Vegas," Sisolak tweeted. "Kathy and I send our love and condolences to Tony's family and friends during this difficult time."