At age 77, Sylvester Stallone is still making movies--and his latest, a documentary called "Sly" that released November 3 on Netflix, is the closest he has come to talking about the 2012 death of his son Sage.

Sage Stallone was an actor, director and producer following in the footsteps of his legendary father when he died of a heart attack at age 36. As a teen, he played the part of Rocky's son in "Rocky V."

Sources close to Sage said he had a prescription drug addiction, ate a lot of junk food, and didn't exercise. An autopsy showed only a small amount of hydrocodone in his system and advanced atherosclerosis, or hardening of the arteries, as his cause of death.

"Agonizing loss"

His father has not talked about the loss of his son, other than to ask for privacy in an attempt to shut down the rumors.

"I am imploring people to respect my wonderfully talented son's memory and feel compassion for his loving mother, Sasha, because this agonizing loss will be felt for the rest of our lives," he continued. "Sage was our first child and the center of our universe, and I am humbly begging for all to have my son's memory and soul left in peace."

According to the documentary's director, Thom Zimny, he didn't mention Sage by name in the documentary, but he did talk about the cost of his career to his family.

Zimny said he and Stallone had a "no boundaries" rule in place while filming. In the final cut, Zimny juxtaposed images of Sage with his father while Stallone was talking about how his family may have been shortchanged while he pursued a demanding career.

"Almost too personal"

It was Stallone who got Sage the part of his son, seeking to give his son the easy start in Hollywood that he never had.

Still, the part may have intersected with reality in the movie, which portrays Rocky's son as feeling abandoned by his father as he mentors another boxer.

"You know, unfortunately, you put things before your family, and the repercussions are quite radical and devastating," he said, admitting that he drew from his own experience in making the film and calling it "almost too personal."

It became a theme throughout the documentary, the importance of family and the risk of losing time and experience with family while working.

His career

Stallone appeared in "Expendables 4" this year, as well as the TV series "Tulsa King" and "Guardians of the Galaxy Vol. 3." He has worked steadily in Hollywood since his first "Rocky" movie in 1976.

He says in the documentary that he had all but given up on a film career when he got that part.

The movie catapulted him to immediate fame--the documentary noted that applause from the movie could be heard on the street in many theaters.