HBO chairman and CEO Richard Plepler is exiting the company.

Plepler made the announcement to staff in a memo on Thursday. “Hard as it is to think about leaving the company I love, and the people I love in it, it is the right time for me to do so,” he wrote. “In the past weeks, I’ve thought a lot about the incredible journey of this company in the nearly 28 years that I have been blessed to be here. It’s a journey of great pride and accomplishment because so many of you, and many others before us, have made HBO a cultural and business phenomenon.”

News of Plepler’s exit comes after it was reported that former NBC Entertainment chairman Bob Greenblatt has been in talks with WarnerMedia CEO John Stankey for a position in which Greenblatt would oversee HBO, Turner, and WarnerMedia’s planned direct-to-consumer service.

“Richard is one of the most successful executives in our industry and I have been fortunate to have his support over the last months,” Stankey said in a statement to Variety. “His vision, energy and passion helped to elevate HBO’s brand to what it has become today. Richard’s impact to our business and on the passionate viewers of HBO’s enduring programming will continue to be felt for years.”

A high-ranking source at WarnerMedia had told Variety that Plepler and Turner president David Levy have grown agitated as WarnerMedia continued to consider changes that could include combining HBO and Turner in which a significant number of redundant jobs would be eliminated.

Plepler first joined HBO in 1992. He served as co-president from 2007 to 2012 before being upped to chairman and CEO upon the retirement of Bill Nelson. During his time at the company, he has greenlit hit shows such as “Game of Thrones,” “Veep,” “True Blood,” and “The Newsroom.” He also oversaw the launch of both streaming platforms HBO Go and HBO Now during his time at the helm.

As Variety previously reported, staffers at Turner have begun bracing for major changes after the last remaining legal challenge to AT&T’s $85.4 billion acquisition of Time Warner was cleared. The first sign of major changes on the horizon came in December when TBS & TNT head Kevin Reilly was named to oversee content for the WarnerMedia streaming service.

Read Plepler’s full memo below.

My dad always gave the best advice. Whenever there was a difficult decision to make, he counseled that since no one could ever have perfect visibility into the future, the best thing you could do was trust your instincts. It has been a touchstone for me throughout my life, and I have found myself returning to it again recently as I think about what is an inflection point in the life of this wonderful company. Hard as it is to think about leaving the company I love, and the people I love in it, it is the right time for me to do so.

In the past weeks, I’ve thought a lot about the incredible journey of this company in the nearly 28 years that I have been blessed to be here. It’s a journey of great pride and accomplishment because so many of you, and many others before us, have made HBO a cultural and business phenomenon. Thanks to all of you, we are today churning on all cylinders both creatively and as a business. Thanks to all of you, I can move on to the next chapter of my life knowing that the best team in the industry remains here to carry on our continued progress and success. As I have said before, this is the team of teams.

It has been the great joy of my professional life to share this ride with you over these many years. And the great honor of my professional life to be your CEO. I don’t have the words to express my gratitude for the support and talent that made our success together possible. But suffice it to say, my love for this place, and for all of you, is deeply a part of me and will last a lifetime. I look forward over the coming weeks to thanking as many of you as I can for the thousands of contributions big and small that have made “this thing of ours,” to quote Tony Soprano, so special. I have told John, who has been nothing but gracious since we spoke, that I would work closely with him to assure a seamless and organic transition.

We’ve created a great and unique enterprise and I know that you will protect its legacy and do all to enhance its future in the years to come.

Know that I will always be cheering loudly, even when I am outside this building, as HBO continues to thrive.

With respect, admiration, and gratitude,

Richard

Plepler’s departure marks the latest major executive exit in the premium cable world, following the recent departure of Starz president/CEO Chris Albrecht and the firing of CBS CEO Leslie Moonves, whose direct reports included Showtime.