Tim Cook is stepping down as the CEO of Apple and transitioning to a role as the company’s executive chairman, effective September 1, the company announced on Monday. John Ternus, Apple’s senior vice president of hardware engineering, will replace Cook as CEO.

Cook’s departure had been speculated upon in recent months, with Apple being perceived as lagging in AI developments in an era when every other Big Tech company has thrown significant resources and billions of dollars in capital expenditure at developing advanced AI.

Cook’s time as CEO of Apple will still be marked by tremendous growth for the company. When he took over as CEO, the company’s market capitalization was around $350 billion; it is now north of $4 trillion. Some of the projects developed under Cook, such as Apple’s self-driving car, failed to gain traction and were ultimately shuttered. At the same time, Apple’s accessories unit, which include the best-selling Apple Watch and AirPods, and its services business, which keeps consumers locked into Apple hardware, were advanced during Cook’s tenure.

Cook first joined Apple in 1998, hired directly by Steve Jobs to be the company’s head of global operations. The now-65-year-old maintained a close working relationship and friendship with Jobs, and when the latter stepped down in August 2011—and passed away two months afterwards—Cook was the natural successor.

Ternus, 50, has worked for Apple since 2001 and served as senior vice president of hardware engineering for the past several years, reporting directly to Cook with increasing responsibility. When he takes over as CEO, he will also join Apple’s board of directors.

In a statement, Cook said “Ternus has the mind of an engineer, the soul of an innovator, and the heart to lead with integrity and with honor.”

This is a developing story. Please check back for updates.