A top executive at Kakao Corp., the operator of South Korea’s top mobile messenger KakaoTalk, will step down. His resignation comes after a fire at a data center led to a mass outage over the weekend and disrupted services for its messenger’s 53 million users worldwide.

Co-CEO Namkoong Whon apologized following the outage and said he would resign.

“I feel the heavy burden of responsibility over this incident and will step down from my position as CEO and lead the emergency disaster task force overseeing the aftermath of the incident,” Namkoong said at a press conference at the company’s office in the outskirts of Seoul on Wednesday.

“We will do our best to restore our users’ faith in Kakao and make sure incidents like these never happen again,” he said, according to a CNBC translation.

Namkoong was appointed CEO in March, according to the company’s website. Kakao reported 47.5 million monthly active users in South Korea during the second quarter. That’s more than 90% of South Korea’s population of 51.74 million people, as of Nov. 1, 2021.

Hong Eun-taek, who led the company alongside Namkoong as co-CEO, will remain the sole head of the company, according to a company filing.

“We sincerely apologize to all those that have suffered from the disruptions during the outage,” Hong said as he bowed alongside Namkoong.

Shares of the company traded 4% higher in South Korea’s morning session ahead of the press conference.