Porn Star Seth Peterson Dead at 28

Adult-film actor Seth Peterson has died, his fiancé confirmed Saturday on social media.

Cyrus Stark -- who also makes adult content under the name Kobe Marsh -- announced Seth's death on X, writing ... "It is with a heavy heart that I share the passing of my Fiance and best friend Seth. I’m truly at a loss for words, and my heart is broken."

He signed it Kobe and shared a link to the GoFundMe he created in Seth's memory ... where he shared that Seth was "found in our home earlier today."

He continued ... Seth was "deeply loved and will be profoundly missed," writing that the money raised through the crowdfunding page will go toward funeral costs.

Seth was 28.