Shellshock, whose real name was Seth Binzer, died at a residence Monday, according to the coroner's online records.
Additional details were not immediately available, and the cause of death was listed as "deferred," pending additional investigation.
Crazy Town's 2000 song "Butterfly" spent two weeks on the Billboard Hot 100.
Word of Shellshock's death immediately prompted an outpouring of support from fans on social media.
"so many big plans have left with you," @sabinamachofficial wrote in the comments section of a memorial post on Crazy Town's official Instagram account. "a very kind, supportive, generous, incredibly honest, talented guy"
Aida Campos Sanchez wrote on Facebook: "I met him at a tattoo convention once. Sweet guy but unfortunately he had a lot of demons inside that he couldn't battle. May he R.I.P"
Shellshock and Bret Mazur co-founded Crazy Town in the mid-1990s, with Adam "DJ AM" Goldstein later joining the group.
The band sold more than six million copies of their debut album "The Gift of the Game," released in 1999.
After Crazy Town released their second studio album "Darkhorse" in 2002, Binzer and Mazur parted ways.
Shellshock went on to work as a songwriter, producer and sound mixer for bands including The Plain White Tees, Julien K and Hollywood Undead, among others, according to the band's biography on their Facebook page.
Shellshock had been open about his struggles with substance abuse, most notably through his appearances on the 2008 season of "Celebrity Rehab with Dr. Drew" and on two seasons of "Sober House" between 2009 and 2010.
"I have a really good group of people around me," Shellshock said on a 2023 episode of the Punk Rock MBA podcast. "I'm very grateful to be here."
He added that he was continuing to make music, describing it as something that has "become my therapy for myself. Even if no one gets it and it helps me, then I guess it's good. And if people love it, that's even better."
Earlier this year, Shellshock re-released a remix of "Butterfly" in a collaboration with the rock band Black Oxygen called "Butterfly (New Anthem)." He also released an EP in March titled "Flirting With Disaster" under the band name Crazy Town X, alongside band members Mark_CXT, DJ Rick One and Sean Heenan.
Shellshock reflected on his sobriety in one of his final Instagram posts, writing in April that he was "grateful."
"I'm a lover than a fighter," he wrote. "But the one I need to love more Instead of fight with is myself."
The CNN Wire contributed to this report.