Shares in Twitter have declined 3% in morning trading on the news that COO Anthony Noto has resigned to become CEO at online lender Social Finance.

Noto joined Twitter in July 2014 after working at Goldman Sachs. Before his role as COO at Twitter, he also served as CFO. The company said other execs will take on Noto’s oversight of ad sales and business operations.

Twitter CEO Jack Dorsey tweeted: “I’m really sad to see Anthony Noto leave us, but I’m happy for him and really proud of everything he’s accomplished at Twitter. He’s been a friend, partner and mentor to me for years. He always has my support and gratitude. Thank you Anthony! We love you.”

Noto gained notoriety in his Twitter role shortly after arriving at the company. In early 2015, his account started tweeting spam messages after it was hacked. Months earlier, he mistakenly sent tweets out about the company’s M&A strategy, having mistakenly thought they were direct messages.

In time, though, he became an effective collaborator with Dorsey, the co-founder of the company who returned as CEO in 2015. Twitter’s management team has recently seemed to quiet loud skepticism about the social media originator’s prospects of increasing revenue and strengthening its bond with users. The company’s share price reached a 52-week high of $25.85 earlier this month, though it has since given up ground.