Actor Sylvester Stallone and son Sage attend the "Rocky V" West Hollywood Premiere on November 13, 1990 at the DGA Theatre in West Hollywood, California. Credit: Ron Galella, Ltd./

Appearing in a pre-taped interview on Good Morning America August 14, Sylvester Stallone, 66, spoke for the first time about his son Sage's death. The action star's filmmaker and actor son, 36, was found dead in his California home July 13.

"It's tough. It's very very tough," Sylvester said while promoting The Expendables 2. "It's a horrible situation but, time, hopefully will heal and you try to get through it. It's something that's a reality in life."

Focusing on work has helped Sylvester heal, the movie star added. "It's important to get back and try to start re-living your life. Otherwise you can go into a spiral."

Sage, who made his movie debut alongside his father in Rocky V, was one of two sons from Sylvester's first marriage to Sasha Czack. He was laid to rest July 21 at St. Martin of Tours Catholic Church in the upscale Brentwood area of Los Angeles. The cause of Sage's death is not yet known.

On August 13, Sylvester and his family -- including wife Jennifer Flavin, 44, and daughters Sophia, 15, Sistine, 14, and Scarlet, 10 -- attended the London premiere of The Expendables 2 sponsored by Netflix. Sylvester's son, Seargeoh, 33, was not present.

The Expendables 2 is in theaters August 17. It also stars Liam Hemsworth, 22, Jason Statham, 44, Jet Li, 49, Jean-Claude Van Damme, 51, Bruce Willis, 57, Arnold Schwarzenegger, 65, Chuck Norris, 72, Terry Crews, 44, and Dolph Lundgren, 54.