Whole Foods Market Chief Executive Officer John Mackey will step down next year, marking a changing of the guard at the grocery chain Amazon acquired four years ago.

Mackey will be succeeded in September 2022 by Jason Buechel, who joined the company in 2013 and has been serving for the last two years as chief operating officer, Mackey said in a note to employees posted on the company’s website. Before joining Whole Foods, Buechel was managing director with consultant Accenture’s retail operations practice. 

Mackey co-founded a natural foods store, called Safer Way, in Austin, Texas, in 1978. A merger with another natural grocer two years later led to the first Whole Foods Market store. As it expanded into a nationwide franchise in the U.S., his chain was credited with helping to popularize organic food. 

That business grew more difficult as large mainstream grocers started stocking their own shelves with organic and natural products. Under pressure from an activist investor, Mackey brokered the sale of his company to Amazon for $13.7 billion in 2017. Despite fears among mainstream supermarket chains that the acquisition would help Amazon dominate yet another industry, the company has struggled to crack the code on physical retail. 

Earlier this month, Whole Foods said it would start charging a $9.95 delivery fee across the U.S., ending a perk the chain had offered Prime subscribers. The charge is a sign that even Amazon continues to struggle with the economics of food delivery. 

“Jason was my personal choice to replace me as the CEO and I’m pleased Amazon leadership agreed that he is the right person for the role,” Mackey said in his note.