Javier Soltero. (Photo via LinkedIn)

Javier Soltero, the leader of Microsoft’s Cortana division, is leaving the company.

Soltero confirmed his departure on Twitter after it was first reported by ZDNet’s Mary Jo Foley Tuesday morning. Soltero has been with Microsoft for four years, according to his LinkedIn profile, and he has served as the corporate vice president for Cortana for the last nine months.

In his tweets, Soltero didn’t say why he was leaving the company but Microsoft in a statement wished him good luck as “he returns to his entrepreneurial roots.”

“I am deeply optimistic that Microsoft will continue to grow by building great products for people around the world,” Soltero wrote on Twitter. “I’m grateful to have learned so much about what it really takes to have massive scale success & look forward to putting these lessons to work on something new.”

Microsoft issued the following statement on Soltero’s departure.

“We are grateful for Javier’s impact and strategic leadership over the last four years at Microsoft, and wish him well as he returns to his entrepreneurial roots. Bringing together all of our work in natural language, intelligence and assistance — including Cortana — enables us to innovate faster for developers, partners and customers.”

Soltero joined Microsoft in 2014 after it acquired an email startup he led called Acompli. He started as a general manager of Outlook Mobile before moving up to the corporate vice president level, first handling Outlook, then the entire Office Product Group and then Cortana.

News of Soltero’s departure comes just a few weeks after another key member of the Cortana team left Microsoft. Samuel Moreau — who spent 11 years with Microsoft, most recently as partner design director of Cortana and artificial intelligence — joined Expedia Group in October as the vice president of global design and user experience.

Foley reported that Soltero’s departure comes as part of the company’s engineering reorganization announced earlier this year. Cortana is moving from the company’s AI + Research Unit to the Experiences & Devices team that is led by Executive Vice President Rajesh Jha.

Microsoft has been building up Cortana as a competitor to AI assistants like Amazon’s Alexa and Apple’s Siri, with a specialty in handling workplace tasks like calendar and email integrations. At the same time, Microsoft and Amazon have been steadily unveiling new integrations between Alexa and Cortana, the fruits of a surprising alliance announced last year.

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