UPDATE: 5:15 PM PT: Sylvester Stallone's rep, Michelle Bega, tells TMZ, "Sylvester Stallone is devastated and grief-stricken over the sudden loss of his son Sage Stallone. 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."

b6:04 PM PT: Now here's a crazy picture -- the L.A. County Coroner van, flanked by a celebrity tour filled with snap-happy tourists. Welcome to Hollywood, folks.

Sage Stallone -- Sylvester Stallone's son -- has died and sources tell us the cause was an overdose of pills.

The details surrounding the death are still unclear .. but we're told he was found in his L.A. home by either a maid or his girlfriend. Paramedics were called to the home and pronounced him dead at the scene.

Sources tell us authorities are trying to determine if the death was intentional or accidental.

We're told Sylvester is a "wreck."

Sage famously made his film debut alongside his father in the 1990 movie "Rocky 5" -- playing the role of Rocky's son Robert Balboa.