Kim Shattuck—the singer, songwriter, and guitarist behind the Muffs—has died. Her husband confirmed the news on social media, saying she passed after a two-year battle with ALS. She was 56. “My heart is forever broken,” wrote Shattuck’s former Muffs bandmate and longtime collaborator Melanie Vammen.

“We are very sorry to announce the passing of our bandmate and dear friend Kim Shattuck,” the Muffs’ Ronnie Barnett and Roy McDonald said in a statement. “Besides being a brilliant songwriter, rocking guitarist and singer/screamer extrodinaire, Kim was a true force of nature. While battling ALS Kim produced our last album, overseeing every part of the record from tracking to artwork. She was our best friend and playing her songs was an honor. Goodbye Kimba. We love you more than we could ever say.” The Muffs’ next album No Holiday is set for an October 18 release.

Shattuck and Vammen were members of the Pandoras in the 1980s. In 1991, they started the punk band the Muffs and released their first singles “Guilty” and “New Love” that same year. A 1992 single on Sub Pop, “I Need You,” followed in 1992, and their self-titled debut album was released in 1993 via Warner Bros. Records. Their cover of Kim Wilde’s “Kids in America” famously appeared on the Clueless soundtrack in 1995.

Four albums followed: 1995’s Blonder and Blonder, 1997’s Happy Birthday to Me, 1999’s Alert Today Alive Tomorrow, and 2004’s Really Really Happy. The group went on hiatus. Shattuck collaborated with other musicians and bands over the years, including NOFX, the Dollyrots, and more. She was briefly a touring member of the Pixies following Kim Deal’s departure from the band. The Muffs returned for various live performances before releasing 2014’s Whoop Dee Doo.

Earlier this year, Shattuck and Vammen’s new band the Coolies released the Uh Oh! It’s...The Coolies EP. All of the proceeds for the EP went to ALS research, and the band made the announcement without Shattuck revealing that she had been suffering from ALS herself. “Sadly, it runs in my damn family, and that disease is a mystery to just about every scientist,” Shattuck said in an interview with Vents Magazine. “We are definitely interested in finding a cure for ALS! Cure it already!”

This article was originally published on October 2 at 7:26 p.m. Eastern. It was last updated at 9:02 p.m. Eastern.