King was responsible for overseeing Walmart's technology shift, which centers on an e-commerce driven model of retail. King's last day at Walmart will be March 29.
Walmart shares were down 0.096% to $98.54 Thursday morning.
"People all have their own perceptions of Walmart," King told CNBC. "For years now ... I've wanted people to understand we are building a tech organization," he said. "I've got a machine learning team. We have some of the best apps in the world."
The memo obtained by CNBC said King will be starting a "new adventure," but didn't specify.
Walmart, in its latest quarter, said digital sales grew 43% from last year, almost doubling sales in the digital channel over the past two years as it continues to define itself as a leader in online grocery sales.
How Much Money Will I Need to Retire?
Want to learn about retirement planning from some of the nation's top experts? Join TheStreet's Robert "Mr. Retirement" Powell live in New York on April 6 for our Retirement Strategies Symposium. For a limited time, tickets are available for $99 for this full-day event. Check out the agenda, learn about the speakers and sign up here.