Not every co-founder is acknowledged at the companies that they help to launch. Sometimes, they quit or they’re elbowed out. Often, they’re conveniently written out of the company’s history.

In the case of Cloudflare, a third co-founder who began the company with its higher-profile CEO, Matthew Prince, and its COO, Michelle Zatlyn, is little known outside the company for a very different reason. As Cloudflare states in an S-1 IPO filing that it made public today, “Tragically, Lee stepped down from Cloudflare in 2015, suffering the debilitating effects of Frontotemporal Dementia, a rare neurological disease.”

Frontotemporal dementia impacts between 50,000 and 60,000 Americans, according to a rough estimate cited by the Alzheimer’s Association, and it tends to impact younger people, often beginning in their 40s.

Though the cause isn’t known, a person’s risk for developing frontotemporal dementia — wherein the frontal and temporal lobes of the brain shrink — is higher if there’s a family history of dementia, according to the Mayo Clinic.

Cloudflare did not respond today to questions about Holloway, but Prince and Zatlyn, in a section of the filing addressed to potential shareholders, credit Holloway as the “genius who architected our platform and recruited and led our early technical team.” In fact, they write, when picking a code name for the company’s IPO, they chose “Project Holloway” to honor his contribution, because the “technical decisions Lee made, and the engineering team he built, are fundamental to the business we have become.”

Holloway’s beneficiaries will be rewarded for that work. According to the S-1, trusts affiliated with him own 18% of the company’s Series A shares (or common shares) and 3.2% of the company’s total outstanding shares. Prince meanwhile owns 20.2% of the company’s class B shares and 16.6% of all outstanding shares, and Zatlyn has 6.8% of the company’s class B shares and 5.6% of the overall shares outstanding.

If Cloudflare goes public at the $3.2 billion valuation that it was last assigned by its private investors, Holloway’s family and other trust recipients could see upwards of $100 million.

That’s none too shabby for a computer geek who attended Monte Vista High School in Cupertino, Calif., before working as an engineer at the bubble-era home improvement site HomeWarehouse.com. Its assets were sold in 2000 to Walmart.com in an apparent fire sale; at the time, then-CEO Jeanne Jackson told the San Francisco Chronicle that Walmart was “very impressed with the commerce platform developed by the Homewarehouse.com team.”

After that experience, Holloway headed to UC Santa Cruz, where he studied computer science and, in a meeting that would change his life, was introduced through a professor to Prince with whom he began building an anti-spam startup called Unspam Technologies. Holloway was its chief software architect; Prince continues to serve as chairman.

The two also co-created Project Honey Pot, an open-source community that still tracks online fraud and abuse.

Zatlyn would enter the picture soon after.

According to Cloudflare itself, in 2009, Prince had taken a sabbatical from work to get his MBA from Harvard Business School. It was when he began telling Zatlyn, a classmate, about Project Honey Pot and its community of users that she helped him recognize a related opportunity in not just tracking internet threats but also stopping them.

While they worked on the business plan as part of their studies, Holloway built the first working prototype. It worked well enough that by 2010, they were pitching investors at a TechCrunch Disrupt as one of the event’s “battlefield” participants.

Holloway wasn’t onstage for that demonstration. He might have preferred to operate in the background given the nature of his work.

Indeed, in the first of just three tweets he has ever published, he wrote simply, “Pondering the nature of web exploits.”

Pictured above: Cloudflare co-founders Zatlyn, Holloway and Prince.