Tripp Smith, one of the most senior executives at Blackstone Group LP and a co-founder of GSO Capital Partners, is leaving the firm.

The 52-year-old plans to pursue other opportunities but will remain with GSO until the end of June, according to an internal memo seen by Bloomberg. Blackstone acquired and integrated GSO -- which refers to the last name initials of Bennett Goodman, Smith and Doug Ostrover -- in 2008. The group, which managed about $10 billion at the time, has expanded to oversee $138 billion as of Dec. 31, making it one of the largest credit investors in the world and Blackstone’s biggest business by assets. Ostrover left in 2015.

“After 13 years with GSO, my co‐founder and great friend, Tripp Smith, has decided to leave,” Goodman wrote in the memo. “Tripp has been instrumental in building GSO into one of the largest and most successful credit investment platforms in the world.”

Few other eras in Blackstone’s history have seen such a changing-of-the-guard among the firm’s top ranks. In June, the former head of the firm’s energy debt practice Dwight Scott became president of GSO as the firm paved the way for future management succession. In January, Blackstone said John McCormick would take over management of the hedge fund business as Tom Hill stepped into the role of the group’s chairman.

The firm also recently announced it was promoting Jon Gray to president and chief operating officer. Ken Caplan and Kathleen McCarthy were promoted to global co-heads of real estate.

Last year, Smith purchased a stake in English soccer club West Ham United F.C., which faces the risk of relegation from the Premier League this year after a string of poor results.

This article was provided by Bloomberg News.