Susan Wojcicki, who served as CEO of YouTube for nine years and was one of Google’s first hires, died on Friday at age 56 after a battle with cancer, her family announced.

Wojcicki’s husband, Dennis Troper, announced her death in a post on Friday evening on Facebook.

“It is with profound sadness that I share the news of Susan Wojcicki passing. My beloved wife of 26 years and mother to our five children left us today after 2 years of living with non-small cell lung cancer,” Troper wrote in the post. “Susan was not just my best friend and partner in life, but a brilliant mind, a loving mother, and a dear friend to many. Her impact on our family and the world was immeasurable.”

“We are heartbroken, but grateful for the time we had with her. Please keep our family in your thoughts as we navigate this difficult time,” he added.

Wojcicki joined Google in 1999 as the company’s 16th employee, becoming the search engine’s first marketing executive. She helped launch Google Video and oversaw the company’s 2006 purchase of YouTube, a then-fledgling rival video-upload site, Variety reported.

She was named CEO of YouTube in 2014 and led the video-sharing platform through immense growth. She stepped down in February 2023 to “start a new chapter focused on my family, health, and personal projects.”

YouTube CEO Neal Mohan paid tribute to his predecessor in a post on social media.

“I had the good fortune of meeting Susan 17 years ago … I am forever grateful for her friendship and guidance,” Mohan wrote in part. “I am forever grateful for her friendship and guidance. I will miss her tremendously. My heart goes out to her family and loved ones.”

Sundar Pichai, the CEO of Google and Alphabet, said in a post on that he was “unbelievably saddened by the loss” of Wojcicki.

“She is as core to the history of Google as anyone, and it’s hard to imagine the world without her.” Pichai wrote. “She was an incredible person, leader and friend who had a tremendous impact on the world and I’m one of countless Googlers who is better for knowing her. We will miss her dearly. Our thoughts with her family. RIP Susan.”

Wojcicki was born on July 5, 1989 in Santa Clara, California. Her father, Stanley Wojcicki, was a physics professor at Stanford and her mother, Esther Wojcicki, was a teacher. She attended Harvard University and earned a masters degree in economics at the University of California, Santa Cruz. She received an MBA from the UCLA Anderson School of Management.

Wojcicki is survived by her husband and four children. Her son Marco, 19, died of a drug overdose at UC Berkeley in February.