Angus Cloud, the actor best known for playing the drug dealer Fezco “Fez” O’Neill on HBO’s “Euphoria,” died Monday in Oakland, Calif. He was 25.

The Oakland Fire Dept. said it responded to a medical emergency at approximately 11:30 a.m., and the patient was “already deceased.” The cause of death was unknown, the fire department said. The Oakland Police Dept. confirmed that it remains an “active death investigation.”

“It is with the heaviest heart that we had to say goodbye to an incredible human today,” Cloud’s family said in a statement. “As an artist, a friend, a brother and a son, Angus was special to all of us in so many ways. Last week he buried his father and intensely struggled with this loss. The only comfort we have is knowing Angus is now reunited with his dad, who was his best friend.  Angus was open about his battle with mental health and we hope that his passing can be a reminder to others that they are not alone and should not fight this on their own in silence.”

The story of “Euphoria,” early on, was that of a young woman who’d shed most of her childhood friends in getting lost in addiction, and found herself forced to make new connections — both drug hookups and sources of real affection and fellow-feeling. How lucky she was as a character to find Fezco, and how lucky we were to have Cloud illuminating their journey together. “Euphoria” is a show about the grandest of human emotions, played out on a high-school stage because it’s only teenagers, perhaps, who allow themselves to decompensate quite so grandly. And Cloud, a remarkably promising talent cut short, was the show’s great stoic. It was his performance, perhaps more than any other on the show, that convinced you that all these kids would be OK. It’s not that what they were going through wasn’t real. But if Rue, at least, had a friend this honest, played by Cloud this honestly, in her corner, she might eventually figure it out.

Fezco dealt drugs to Zendaya’s Rue, but, somehow, he read as something other than an enabler — he was, indeed, one of a few people in her life who pushed her toward admitting to herself who she was. That way, even if she couldn’t fix her issues alone, she might at least know what they were. Cloud’s approach to these conversations was through a sort of startling plainspokenness, a process of seeming to seek the most ethical thing to say that made the struggle of figuring that out clear.

He had a code, and it was a moral one. Through his pure and honest performance as Fezco, we got to know Cloud, which means anyone who watched the show feels this loss.