(Photo credit: Joe Marquette/AP Photo)

Sean Sasser, who appeared on MTV's "The Real World: San Fransisco," has died, his former co-star Judd Winick announced on Twitter. He was 44.

"Our friend Sean Sasser has died. Our love goes out to his family & husband Michael. We will miss u so much," Winick wrote.

According to his partner, Michael Kaplan, Sasser, who was HIV-positive, died of mesothelioma, a form of lung cancer, Queerty reported.

In the 1990s, Sasser appeared on the MTV reality show with his late partner Pedro Zamora - and afterward, he worked tirelessly as an AIDS activist.

"'The Real World' and Pedro was the first opportunity for America to look at HIV and AIDS as a young disease, as something that young people deal with," Sasser said at the time.

Recently, the Washington Blade reported that Sasser had been working as a pastry chef at the D.C. restaurant Ris.

"I want to serve desserts and pastries that people recognize and love to eat, but sometimes with an unexpected twist of surprise," he said.