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Sylvester Stallone's son, Sage Stallone, has been found dead at his home in Los Angeles.

"Sylvester Stallone is devastated and grief-stricken over the sudden loss of his son Sage Stallone," a rep for Sly tells ET. "His compassion and thoughts are with Sage's mother, Sasha. Sage was a very talented and wonderful young man, his loss will be felt forever."

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Sage's attorney George Braunstein was first to confirm the sad news, revealing that the 36-year old "was in good spirits" and planning his wedding in the days leading up to his untimely passing.

The cause of death is as of yet unknown, but is believed to be accidental. Ed Winter of the Los Angeles County Department of Coroner told the press Friday night that there is an ongoing death investigation, and that an autopsy will be conducted in the next few days. According to Winter, Sage was found unresponsive by a housekeeper and an undisclosed family member. Neither of his parents came to the home, but they were both informed of his death, Winter also said. There were prescription pill bottles found at the home, but Winter didn't go into more detail on that subject, though he said earlier that no open bottles had been found. There were no signs of foul play or a suicide note.

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Sage was among Sylvester's five children, and one of two sons from his first marriage to Sasha Czack.

The young Stallone was an actor, following in his father's footsteps from an early age. Sage made his debut alongside his father in the fifth installment of the Rocky franchise where he played the son of Rocky Balboa. He also appeared with his father in the 1996 film Daylight.