The Hollywood actor's eldest son, Sage, from his marriage to Sasha Czack, was found dead at his home in Los Angeles on Friday (13Jul12).
A post-mortem examination on Sunday (15Jul12) proved inconclusive and family members will now have to wait up to six weeks for the results of toxicology tests to find out what happened to the 36 year old.
Stallone has now spoken publicly for the first time about the tragedy and released a moving picture showing him embracing Sage as a youngster.
The Rocky star tells TMZ.com, "When a parent loses a child there is no greater pain. Therefore I am imploring people to respect my talented son's memory and feel compassion for his loving mother Sasha. This agonising loss will be felt for the rest of our lives. Sage was our first child and the centre of our universe and I am humbly begging for all to have my son's memory in full left in peace."