Dick Costolo Out as CEO of Twitter Co-founder Jack Dorsey will temporarily replace him as the company searches for a new chief executive.

On July 1, Dick Costolo will step down as chief executive of Twitter, the company announced today. Co-founder, chairman and former CEO Jack Dorsey will replace Costolo in the interim as the company searches, both internally and externally, to fill the role.

In a statement, Costolo said there is "no one better" than Dorsey to lead Twitter at this time. "He has a profound understanding of the product and Twitter's mission in the world as well as a great relationship with Twitter's leadership team. I am deeply appreciative of the confidence the Board, the management team and the employees have placed in me over the years, and I look forward to supporting Twitter however I can going forward."

Costolo and Dorsey also exchanged supportive tweets.

Welcome back, @jack !! https://t.co/3papmyUKg0

— dick costolo (@dickc) June 11, 2015

Thank you for everything @dickc! You're a selfless leader who's built an amazing team and company #proud https://t.co/52z4TIYIUh

— Jack (@jack) June 11, 2015

Dorsey – who will remain CEO of Square, the payments company he co-founded in 2009 -- served as Twitter's first CEO from May 2007 to October 2008, when he was replaced by Evan Williams. Two years later, Williams was replaced by Costolo, who was COO at the time.

This latest shakeup is not altogether unsurprising: Costolo has increasingly come under scrutiny, both for the company's sluggish user growth and its failure to define a clear business strategy. In January, Dorsey unleashed a series of tweets defending Costolo against his critics.

Repeating some of the sentiments contained in that tweetstorm, Dorsey released the following statement: "The future belongs to Twitter thanks in large part to Dick Costolo's dedication and vision. Dick has put a world-class team in place and created a great foundation from which Twitter can continue to change the world and grow. We have an exciting lineup of products and initiatives coming to market, and I look forward to continuing to execute our strategy while helping facilitate a smooth transition as the Board conducts its search."

Related: Twitter's Jack Dorsey Defends CEO Dick Costolo in Massive Tweetstorm