Though he was pronounced dead on the scene Friday, TMZ reports Sage Stallone had actually passed away three to four days earlier.
Sage -- Sylvester Stalone's first child with ex-wife Sasha Czack -- was discovered in his Los Angeles apartment July 13. The 36-year-old is believed to have died from an apparent drug overdose.
According to TMZ, Sage "lived like" the reclusive Hollywood mogul Howard Hughes. Sage often spent days alone in his room, which was "littered with junk," including cigarette butts, beer cans and food. A law enforcement source adds that Sage's room was "disgusting" and reeked of various odors.
Shortly after Sylvester learned of his son's passing, he released a statement via his rep to Us Weekly. "Sylvester Stallone is devastated and grief-stricken," his rep said. "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."
Sage followed in his father's footsteps by making his big-screen debut as a teen in 1990's Rocky V, playing Rocky Balboa's son, Robert. In 2006, he made his directorial debut with Vic, which was shown at the Palm Springs Film Festival. He is survived by his two parents, one brother and three half-sisters.
When news of Sage's tragic passing spread, several Hollywood stars expressed their condolences via Twitter. "RIP Sage Stallone," Shana Moakler wrote. "I only spent time with you briefly and you were/are wonderful... prayers to your family.
Denise Richards added: "My heart goes out to Sylvester and your family."