Jeff Shell is stepping down as CEO of NBCUniversal following a misconduct investigation, which found he had an “inappropriate relationship” with a woman in the company.

Comcast, the parent company of NBCUniversal, and Shell announced the news in a joint statement, saying they have mutually agreed that Shell will depart effective immediately following a third-party investigation into a complaint of inappropriate conduct.

“Today is my last day as CEO of NBCUniversal,” Shell wrote in a memo to staff. “I had an inappropriate relationship with a woman in the company, which I deeply regret. I’m truly sorry I let my Comcast and NBCUniversal colleagues down, they are the most talented people in the business and the opportunity to work with them the last 19 years has been a privilege.”

A successor to Shell has not been named. Shell’s senior team will now report directly to Mike Cavanagh, president of Comcast Corporation. Cavanagh and Comcast CEO Brian L. Roberts announced the change in a statement. A source close to the situation said Comcast is in no rush to find a successor to Shell, nor is the company likely to appoint an interim CEO.

“We are disappointed to share this news with you. We built this company on a culture of integrity. Nothing is more important than how we treat each other,” Roberts and Cavanagh said in a memo. “You should count on your leaders to create a safe and respectful workplace. When our principles and policies are violated, we will always move quickly to take appropriate action, as we have done here.”

The news, which sent shockwaves through the Burbank-based company, is unfolding days ahead of Comcast reporting its first quarter results on Thursday, including a conference call with Wall Street analysts. It’s also shaking out weeks before the TV industry’s annual upfront ad sales season, which could raise eyebrows and questions from advertisers.

Roberts and Cavanagh added, “Please know that NBCUniversal is performing extremely well operationally and financially, and we couldn’t be more enthusiastic about our position and prospects going forward. We are fortunate to have an experienced, world-class group of executives leading this incredible company.”

Succeeding Steve Burke, Shell assumed the role of CEO on Jan. 1, 2020, shortly before the pandemic upended almost every aspect of the company. He reported directly to Comcast CEO Roberts and was responsible for overseeing everything from news and entertainment TV networks, to the film studio, theme parks and other divisions. As NBCUniversal CEO, Shell was also charged with moving the company more heavily into streaming. In recent months, NBCU has gotten more aggressive with Peacock by pushing new sports and news concepts, as well as pricing initiatives on the service.

“Jeff Shell is the ideal executive to take the helm at NBCUniversal,” Roberts said at the time of Shell’s hiring as CEO. “I have worked closely with Jeff for many years and he is an extraordinary leader who inspires loyalty, delivers strong results and cares deeply about our company, its employees and partners. I could not be more confident in his ability to lead NBCUniversal into the future.”

A Comcast veteran, Shell joined the company in 2004 to oversee cable channels from Fox Cable Networks Group. Shell previously spearheaded international operations out of London from 2011 to 2013 before segueing to oversee the Universal Pictures as chairman of NBCUniversal Film and Entertainment.

Shell’s abrupt ouster is another sign that the standards for corporate office behavior have changed over the past six years since the #MeToo reckoning began. His sudden exit from Universal City recalls Jeff Zucker’s sudden fall from the top job at CNN last year after the disclosure of his relationship with a longtime subordinate executive.

Cavanagh, meanwhile, joined Comcast as chief financial officer in 2015, after more than 20 years in the financial services industry, including a long stint as a senior exeutive at JPMorgan Chase. Cavanagh, who was promoted to president of Comcast last fall, has been seen as being positioned to take on more of Roberts’ duties over time. In recent earnings calls, Cavanagh has sounded enmeshed in the nitty gritty of Comcast’s operations.

On Sunday, as the shock of Shell’s resignation reverberated around NBCU and the industry at large, Cavanagh was said to have been on the phone quickly talking to key clients and associates of NBCU. One source said Cavanagh has sought to reassure contacts that he has been involved in the operations of NBCUniversal for some time.

(Brian Steinberg and Cynthia Littleton contributed to this report.)