Actor Kenneth Mitchell, known for his work on "Star Trek," died Saturday, according to StarTrek.com. He was 49.

Mitchell was diagnosed with ALS, a neurodegenerative disease, more than five years ago, according to a statement posted to his Instagram page. According to the statement, he faced "awful challenges" in those years.

"And in true Ken fashion, he managed to rise above each one with grace and commitment to living a full and joyous life in each moment," the statement said. "He lived by the principles that each day is a gift and that we never walk alone."

ALS, also known as Lou Gehrig's disease, affects the nerve cells that make muscles work in both the upper and lower parts of the body, according to the Centers for Disease Control and Prevention. The disease makes the nerve cells stop working and die. 

In the U.S., more than 30,000 people are believed to be living with ALS, and an average of 5,000 people in the country are diagnosed with ALS each year. Most people with ALS live from two to five years after symptoms develop.

On Aug. 10, the actor shared an Instagram post about what living with ALS was like.

"It's been a long 5 years. So much lost, so much gained. Incredibly hard times, mixed with so many more blessings," he wrote. "At the heart of it all are friends and family, caregivers and doctors coming to the aid of my family over and over and over again."

Mitchell first publicly spoke about his diagnoses in a 2020 interview with PEOPLE.

"The moment that they told us it was [ALS], it was like I was in my own movie," Mitchell told PEOPLE. "That's what it felt like, like I was watching that scene where someone is being told that they have a terminal illness. It was just a complete disbelief, a shock."

Mitchell appeared in several roles after his diagnosis. 

He played the Klingons Kol, Kol-Sha, and Tenavik, as well as Aurellio, on "Star Trek: Discovery," according to StarTrek.com. He also voiced several voice characters in an episode of "Star Trek: Lower Decks."

Mitchell was also known for his work in the TV series "Jericho" and "The Astronaut Wives Club" and his acting in "Miracle" and "Captain Marvel."

In the Instagram post announcing his death, Mitchell was remembered him as a daydreamer, nature explorer, cat lover and "more than anything else, a proud father."

Mitchell is survived by his parents, his wife and their two children. According to StarTrek.com, Mitchell asked that any gifts be directed toward ALS research or toward his children.