Gavan O’Herlihy, best known for playing Richie and Joanie Cunningham’s disappearing brother Chuck on “Happy Days,” has died. He was 70.

O’Herlihy died in Bath, England on Sept. 15, his brother, Cormac O’Herlihy, confirmed to Variety. A cause of death was not disclosed, but his brother confirmed that it was not COVID-19.

After making an appearance on an episode of “The Mary Tyler Moore Show” in 1973, O’Herlihy broke out on “Happy Days” as Chuck, the eldest Cunningham sibling. Chuck was a high school jock and was almost always seen carrying a basketball. He was played by three different actors — Ric Carrott in the show’s pilot, O’Herlihy for the first two seasons and Randolph Roberts for two episodes in Season 2 — giving way to the pejorative “Chuck Cunningham syndrome” to describe TV characters who disappeared from shows and were later written off as if they never existed.

Gavan O’Herlihy in “The Descent: Part 2.” ©Lions Gate/Courtesy Everett Collection

After “Happy Days,” O’Herlihy appeared in a string of film and television roles, often playing antagonistic or villainous characters. This included the TV movie “The Ghost of Cypress Swamp” in 1977, the “Amazing Spider-Man” series in 1979, “Superman III” and “Never Say Never Again” in 1983, the “Star Trek: Voyager” series in 1995 and the movie “The Descent: Part 2” in 2009. O’Herlihy’s other credits include appearances in “Twin Peaks,” “The Memoirs of Sherlock Holmes,” “Rich Man, Poor Man,” “Death Wish 3,” “Willow” and “Tales From the Crypt.” O’Herlihy’s most recent film, “Queen of the Redwood Mountains,” is currently in post-production.

O’Herlihy’s “Happy Days” on-screen brother Ron Howard paid tribute to him on Twitter, writing: “RIP Gavan. I knew him as the 1st of 2 Chucks on #HappyDays and then as Airk in #Willow where I had the pleasure of directing him. A talented actor with a big free spirit.”

Beyond Cormac O’Herlihy, survivors include siblings Patricia, Lorcan and Olwen, as well as his wife Juliette and four sons Rogan, Lonan, David and Daniel.