Nicky Wonder, longtime guitarist for Beach Boys legend Brian Wilson and co-founder of the LA power-pop group Wondermints, has died. As Rolling Stone points out, Wilson’s site made a statement on Wonder’s death, claiming that he died in his sleep on Tuesday night. No cause of death has been revealed. Wonder was 59.

Nicky Wonder, born Nick Walusko, co-founded Wondermints in Los Angeles in 1992. They released their self-titled debut in 1995, and they went on to release four more albums, the most recent of which is Kaleidoscopin’: Exploring Prisms of the Past. And they’ve long played a role in the Los Angeles power pop scene, with members of the group collaborating with like-minded bands like Eels and the later-years version of Love. Mike Myers, a fan, brought Wondermints in to contribute to the soundtrack of the 1997 movie Austin Powers: International Man Of Mystery.

But Wondermints’ chief legacy is with Brian Wilson, the troubled and reclusive sonic mastermind of the Beach Boys’ great works. Wilson met Wondermints backstage at a show, when they performed one of his own songs for him. (Wilson reportedly loved it, and he didn’t recognize the song as his own.) The Wondermints essentially became Wilson’s backing band in 1999. And when Wilson released 2004’s Brian Wilson Presents: Smile — the newly recorded version of the much-bootlegged but unfinished and never-released 1966 Beach Boys album Smile — Nicky Wonder and the other Wondermints played on it.

Wonder continued to play with Wilson, both onstage and on record, in the years that followed. Wonder played on many Wilson albums, up to 2015’s No Peer Pressure. Wonder also played on the 2012 Beach Boys album That’s Why God Made The Radio, which served as Brian Wilson’s short-lived reunion with the group.

Here’s Brian Wilson’s statement about Wonder:

Today is a sad sad day.

It is with my deepest regret to tell you that our beloved Nicky Wonder passed away last night in his sleep.

We are in a state of shock as you can imagine.

But we are going to honor him with tonights show.

Nicky was my favorite guitar player ever. I always loved the way he used his fingers. He was a real Rock and Roll guy and great singer too.

He was a friendly and very nice person and he was really really funny. He had the best sense of humor.

We are all crying today, he will be missed beyond words.

Our hearts go out to his wife Susan and his entire family, friends and fans.

We love you Nicky.

Love & Mercy

Brian Wilson

A few examples of Wonder’s work: