After serving Twitter for six years, Jack Dorsey was named chief executive of the social media company.

Dorsey sent a Monday tweet out to his 5.9million followers. He resigned as CEO of Twitter, the social media giant that he co-founded in 2006. Parag, who is also a member of the board and CTO at Twitter, announced that Dorsey would be replaced by Agrawal “starting immediately”. Dorsey explained that his decision to resign was based upon the board’s approval, Agrawal agreeing to serve as the chair and other opportunities for upward mobility.