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Twitter CEO Dick Costolo is stepping down from his role beginning July 1, and Twitter co-founder and current Square CEO Jack Dorsey will take over as Interim CEO.

Costolo, who has been on the hot seat for months, will remain on the company’s board, according to multiple filings submitted with the Securities and Exchange Commission Thursday. Dorsey and Costolo then spoke on a conference call Thursday afternoon to discuss the transition. Dorsey said the decision had nothing to do with the company’s performance. Costolo added that he has been talking with the board about this move since the fall.

"One thing I do want to make clear is that this transition is not the result of anything more than Dick deciding to move on from his role as CEO," Dorsey said. "There is no connection with our near term results."

Even so, Twitter and Costolo have been under the microscope since going public in late 2013, primarily dealing with user growth issues that seemed to imply the company had hit a plateau. Costolo also took flack for overseeing an ever evolving executive team at the company, which included the removal of COO Ali Rowghani, a new CFO, and multiple heads of product all in 2014.

Re/code asked Costolo about his job security multiple times since April, most recently at the annual Code Conference. He consistently dismissed the idea that he was at odds with the board, which Re/code reported in January was losing patience.

"I don’t worry about that at all," he told Re/code in late April. "The board and I are completely in sync. Believe me, I don’t worry about that at all."

Here he is answering a similar question at Code.

The company has not yet named a permanent CEO replacement. Dorsey said that the search process "has not begun yet." Board members Fenton, Peter Currie, and co-founder Ev Williams will lead the search committee, he added, and they will consider both internal and external candidates.

Dorsey will return to the helm of the company he ran in its earliest days. He will continue to work with Square. According to the filing outlining Dorsey’s employment: "Prior to your start date on July 1, 2015, we will develop and agree on a Conflict of Interest Policy as it pertains to your work with Square, Inc." Dorsey said on the conference call that he would "split time" between the two companies for the immediate future.

Costolo made the announcement to company employees at Tea Time on Thursday, Twitter’s weekly all-hands meeting. Sources within the company say the meeting time was initially scheduled for 10 a.m., then bumped to 1 p.m., or after the markets closed.

Dick spoke to the staff followed by Twitter board member Peter Fenton and new CEO Dorsey. Very few members of Twitter’s top brass spoke during the meeting, these people said.

Twitter stock initially spiked almost eight percent on the news, but has lost most of those gains. It’s now up about three percent in after-hours trading.

Here’s a look at some of the reaction on Twitter:

In under five years as CEO, @dickc grew Twitter from a $3b valuation to a $23b valuation. Credit where credit is due. Thanks, Dick. — Chris Sacca (@sacca) June 11, 2015

For being the funniest CEO in the world, #ThankYouDickC. pic.twitter.com/LxZs0gLtlf — Mike Davidson (@mikeindustries) June 11, 2015