LFO, a popular 90s music group known for the smash hit "Summer Girls," has lost one of its founding members.

Brian "Brizz" Gillis died on Wednesday at the age of 47. His cause of death is currently unknown.

Gillis was part of the group in its early days, along with Rich Cronin and Brad Fischetti. He and Cronin founded the band in 1995. Fischetti joined later, and the trio were signed to Lou Pearlman's record label, Trans Continental Records – the same label that signed boy bands like NSYNC and Backstreet Boys.

The group had a bit of success after that, but it wasn't until they released "Summer Girls," a hit also known as "the Abercrombie & Fitch song," that they achieved stardom.

Gillis left the group just before that success came, and he was replaced by Devin Lima. They went on to release another hit, "Girl on TV," with a music video that starred Jennifer Love Hewitt.

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Although the group members were just in their 20s during their heyday, Gillis is actually the third member of LFO to pass away.

Cronin died in 2010 after battling leukemia. He had a stroke after taking a medication to help him recover from complications from a stem cell transplant. He was 36.

Lima died in 2018 of stage 4 adrenal cancer. He was 41.

Fischetti, the last surviving member of LFO, posted a tribute to Gillis on his Instagram page.

"Every story is made up of chapters," he began. "Some develop naturally. Some you have to cut up in your mind. The first two chapters of the LFO story lost a main character yesterday."

"Brian ‘Brizz’ Gillis passed away. I don’t have details and it wouldn’t be my place to share them if I did. I am really struggling to process this tragic loss. I’ve said it before and I will continue to say it; the LFO Story is a tragedy. If you know what I’ve been doing, you know I’m trying to bring light into the darkness. Trying find redemption in pain and suffering. Trying to honor the legacy."

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He called Gillis his "former bandmate and friend," and wrote, "If it wasn’t for his hard work and dedication in the early days of LFO, the first two chapters, the LFO you came to know and (hopefully) love would not exist."

"My relationship with Brian was complex," he continued. "It contained moments of great tribulation but also of great joy. I learned a lot from him about the business of music and how to put together and rock a show. And it’s those positive aspects of our relationship that I will lean on now and forever."

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Fischetti said "I’ve prayed for Brian every day for many years. And I will continue to pray for him, for his beloved father, for his friends, his family, and those who loved him."

In a touching line highlighting the previous band members' deaths, he added, "I know that soon or maybe already, Brizz will be greeted by Rich and Devin. And I hope that together, they will make some sweet sounds. I would really like that."

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He finished his tribute with "Rest east bro. Rest easy."