Jack Dorsey has announced his resignation as CEO of Twitter, the shortform social media platform he co-founded in 2006. He made his intentions known to staff in an email which he tweeted out publicly this morning.

In the email, he assigned Chief Technology Officer Parag Agarwal to replace him as CEO.

He also announced Salesforce president and co-founder Bret Taylor would become Twitter's board chair and that Dorsey himself would remain on the board until May when his term runs out. He had been board chair since initially leaving as CEO in 2008 before coming back on in 2015.

In explaining his reasoning for leaving, the executive said that the company's perceived "founder-led" nature presents as a single point of failure and can be severely limiting to its growth. The company has seen its profits narrow down in the past 2 years with the recent third quarter of this year sinking into loss due to a shareholder class action settlement. Activist hedge fund Elliott Management had called for Dorsey's resignation last year (via CNBC), questioning his ability to run both Twitter and Square, the payments company he cofounded in 2008, at the same time — the dispute resulted in Elliott gaining board members while Dorsey remained as CEO. The social platform had recently launched direct user monetization through its Blue subscription service.

$TWTR shares opened 10% higher today and, as of press time, remains at a 3% gain.

Dorsey remains CEO of Square.