Kim Shattuck, singer-songwriter for the Muffs and a prominent figure in the alt-rock scene of the late ’80s and ’90s, has died at age 56. Shattuck had been stricken with ALS.

Melanie Vammen, a bandmate in the Muffs and a more recent formed group, the Coolies, confirmed the news on social media, saying “My heart is forever broken.”

Vammen reposted a message from Shattuck’s husband, Kevin Sutherland, who posted a wedding photo and wrote, “This morning the love of my life Kim passed peacefully in her sleep after a two year struggle with ALS. I am the man I am today because of her. She will live with all of us through her music, our shared memories and in her fierce creative spirit. I love you forever my Kimmy. Thank you for sharing your life…”

The off-again, on-again Muffs had reunited recently to record their first album in five years, “No Holiday,” an 18-track release set to come out Oct. 18 on Omnivore Recordings.

Ronnie Barnett, her longtime Muffs bandmate, had not yet posted a statement as of this writing, but changed his social media status to “feeling devastated”… and his profile picture to a block of solid black.

Shattuck’s latest band, the Coolies — with Palmyra Delran as well as original Muffs member Vammen taking part — was announced only this past July, with an EP released that same month. At the time, Shattuck and her label announced that 100% of proceeds would go to ALS research, without revealing that she was suffering from it herself.

Asked why they had chosen an ALS research charity by Vents magazine in July, Shattuck responded, “Sadly, it runs in my damn family, and that disease is a mystery to just about every scientist! We are definitely interested in finding a cure for ALS! Cure it already!” In other interviews, she also mentioned that ALS had afflicted her father’s side of the family and “hit a great deal of my family members.”

Wrote her Coolies bandmate Delran on social media Wednesday: “So grateful for her friendship. RIP Sweetest Soul.”

Tributes have begun to come in from famous fans as well as friends.

Said Kay Hanley of Letters to Cleo, “She was an incredible person with the best kind of rock n’ roll life story. I fell under her spell when I saw her swinging from the rafters and shredding her guitar and vocal chords downstairs at the Middle East in Central Square in ‘94. I’ve never seen a band so explosive.”

Wrote Greg Behrendt, the comic and author of “He’s Just Not That Into You”: “RIP Kim Shattuck of the Muffs. Look up and listen to ‘Lucky Guy’ or ‘Sad Tomorrow’ and revel in their pop punk genius. The Muffs are a much overlooked and undernourished band that rival the best of Hole and Green Day. You were a total punk Kim and you will be missed.”

Shattuck rose to prominence as the bass player for the all-female group the Pandoras in the 1980s. “I joined that band when I was really immature and young. I was the bass player and I didn’t really have any say on the direction, so I bided my time,” she told Guitar World magazine. “I practiced writing songs until I got better, ’cause I wanted to write songs really bad, but not in that band.”

She then switched to guitar as she founded and led the pop-punk Muffs, who achieved peak notoriety in 1995 between their sophomore album (cheekily titled “Blonder and Blonder”) and a cover of Kim Wilde’s “Kids in America” included on the “Clueless” soundtrack.

She had mixed feelings about the success of the Wilde cover. “The lyrics are really stupid,” she told the website Culture Brats in 2015. “I just had an attitude about it because I didn’t write it…. It was just kind of weird and awkward for us to play it but once we started playing it, we realized people really enjoy seeing us play that song, and the fact that we didn’t really play it was kind of rebellious for no reason. … Now we play it live sometimes. It was funny. We had never really considered playing it live. It was always a thorn in our side, but we ended up doing it.”

In 2013, Shattuck briefly joined the Pixies on tour as a replacement for the exiting Kim Deal. She was booted from the band without explanation and told Rolling Stone she thought it might have been because the others were “more introverted people” than she was. She indulged in a stage dive in a show at L.A.’s Mayan Theatre, and “I know they weren’t thrilled about that,” she said. “When I got offstage, the manager told me not to do that again. I said, ‘Really, for my own safety?’ And he said, ‘No, because the Pixies don’t do that.'”

The last Muffs album, “Whoop Dee Doo,” was released in 2014. “There is scarcely a more consistent band in all of American pop-punk,” wrote Pitchfork in a review of their return after a decade-long recording layoff. “they haven’t slowed down or softened their attack, or lost their way with tune-construction. Even Shattuck’s voice remains barely touched by time. The scratchy sleepless-night tone she used to reserve for her bloodthirsty end-of-verse howls has crept into most of the rest of her singing, although it’s not unwelcome. … (A)another big part of the Muffs’ charm,” Pitchfork noted, “is Shattuck’s perpetual balancing act between romantic vulnerability and indignant fury.”

Shattuck talked with Guitar World about the preconceptions that came with being a woman in such testosterone-driven genres, as well as a fantasy object for some in the audience. “There were people at the guitar stores who were really stupid about it, thinking I was getting stuff for my boyfriend. I don’t care –- the joke’s on them. But I think people were generally into it. For some people there’s a fetish about it, which is stupid. I used to get really mad at those people. If they got too close to the stage I would literally kick them in the face. Literally! Cause I was just like, I don’t want you to like jack off to me later! I would just kick them,” she said with a laugh.

Although the band was known for a punkier approach, the band’s more Beatle-esque 2014 return, which Pitchfork found “Rubber Soul”-inspired was a return to her roots. Shattuck said she was inspired by John Lennon and, later, the Bangles: “I saw the Bangles before I was in a band. I really liked their rhythm. That was right when I was trying to learn how to play guitar. I was really frustrated because I couldn’t strum, and then I saw Susannah Hoffs do this cool strum on a song, and it was my goal after that to learn how to do that strum.”

In August, the group announced the forthcoming release of “No Holiday” on Omnivore, a label that had previously re-released the group’s first three 1990s albums. Said Shattuck in a statement, “I wrote the songs between 1991 and 2017. We decided to have a long album and use songs that had been in my arsenal but were weeded out for super concise albums. They were all great songs and we didn’t want them to go to waste. No way!”