Kevin Turner who left the Microsoft COO position in July to become CEO of hedge fund Citadel Securities, is already out at Citadel, the company says.

Turner is being replaced by long-time Citadel exec Peng Zhao who currently serves as vice chairman of Citadel.

Zhao had previously been global head of market making for Citadel Securities. He joined the company in 2006 and worked his way up from a senior quantitative researcher role.

Citadel Securities provides automated market making and execution services. It trades products like equities, equity options, and interest rate swaps for retail and institutional clients. The hire of a former Microsoft exec came a time when technology is becoming an increasing part of the financial system.

However, Turner was never a technologist at Microsoft. He ran sales and marketing. And he came from the tight-margin world of retail, cutting his teeth at Walmart, spending nearly two decades there where he worked his way up from a cashier to chief information officer and later president and CEO of the Walmart-owned retailer Sam’s Club.

Turner then spent 11 years at Microsoft and was a major part of former CEO Steve Ballmer's brain trust. Turner was at one time in the running to be named CEO of Microsoft after Ballmer announced his retirement. Obviously, the job went to Satya Nadella instead.

He was known as a tough operator and wasn't particularly beloved at Microsoft by the employees, several Microsoft employees told us. When he left, they took an anonymous chat app called Blind to basically cheer his departure.

A person close to Citadel tells us that Turner sent a nice note to the CS team when his departure was announced and Ken Griffin, CEO of this unit's parent company Citadel, also publicly wished Turner well, sending us this statement:

"I am pleased to announce Peng Zhao has been named CEO of Citadel Securities. I want to thank Kevin Turner for his leadership and the lasting impact he made on our firm. Kevin has made important contributions across many areas of Citadel Securities."

Turner also had polite things to say about Griffin with this statement: "I want to thank Ken Griffin for his friendship and support, and for the opportunity to be a part of one of the most respected financial services companies in the world. I wish him and the entire team continued success."