Sage Stallone, son of famed action star Sylvester Stallone, was found dead Friday (July 13), according to TMZ. He was 36 years old.

While many of the details surrounding Sage Stallone's death remain unclear, a source told the outlet that an overdose of pills was the cause of death, but L.A. police are still trying to determine whether the overdose was intentional or an accident. He was reportedly found by his girlfriend.

Sage Stallone famously appeared opposite his father in "Rocky V" as the iconic character's onscreen son, Rocky Balboa Jr. He later appeared in the 1996 disaster film "Daylight," once again opposite his father. Sage Stallone acted occasionally in the years after, mostly smaller-profile films and only doing one every year or so. He also directed two films and produced one more.

He is the son of Sasha Czack.

TMZ reported that Sylvester Stallone is a "wreck." The action star made his last public appearance Thursday at San Diego Comic-Con. Stallone was there appearing on the panel for his upcoming film "The Expendables 2," in which he stars alongside other icons from the action genre like Arnold Schwarzenegger, Bruce Willis, Chuck Norris and Jean-Claude Van Damme.

The panel at Comic-Con was somewhat of a tribute to Stallone's career in action movies. Before appearing in front of the crowd in Hall H, an extensive montage of some of his greatest onscreen action moments played for the crowd. He talked about hoping to return the over-the-top action genre to its former glory of the 1980s.

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