Christina Miller, the WarnerMedia executive who oversees Cartoon Network, Adult Swim, Turner Classic Movies and Boomerang, will leave the company at the end of the year – the latest departure of a senior executive from the entertainment conglomerate since it has come under the aegis of AT&T.

“This is not a decision I came to lightly,” said Miller, in a prepared statement. “It’s one of the hardest I’ve had to make in my career. Ultimately, it feels like the right time for me to leave and take a little time to think about what comes next, but I do so, feeling immensely proud of the work we’ve done together and so grateful for the experience.”

Michael Ouweleen, executive vice president and chief marketing officer of Cartoon Network, Adult Swim and Boomerang, will serve as the interim president and Miller will help with the transition.

Miller’s departure comes after a reorganization of WarnerMedia assets set in motion after AT&T completed its $85 billion purchase of the storied media company once known as Time Warner. Under that plan, cable networks devoted to kids and family entertainment that were once part of the company’s Turner cable division were placed under the supervision of the Warner Brothers studio.

Since AT&T has started exerting its business plan on the unit, several executives have departed, including Richard Plelper, the former CEO of HBO; David Levy, president of Turner; and Donna Speciale, president of ad sales for WarnerMedia.

Miller led Turner’s kids-and-young-adults division for the past five years, and supervised Boomerang, a subscription streaming-video service that launched in 2017. She most recently was given responsibility of TCM, the cable network that runs classic films.

Prior to her current position, Miller was general manager of NBA Digital and a senior vice president of Turner Sports, where she led the day-to-day operations for the NBA Digital portfolio; managed relationships with league partners; and supervised the strategic planning and scheduling of on-air sports programming and developing marketing programs for the division’s linear and digital properties. She joined WarnerMedia in 2005 as vice president at Cartoon Network Enterprises, where she built the division’s first global consumer products business. She had been a senior vice president of brand management and licensing for HIT Entertainment.