In addition, Braunstein tells PEOPLE, although Stallone smoked cigarettes and consumed candy and soda, the 36-year-old never exhibited any signs of drug use or addiction.
"Sage didn't even drink," the attorney, who knew the son of Sylvester Stallone socially and professionally for more than 15 years, tells PEOPLE. "There was a report that his room was filled with liquor bottles. Actually, they were empty bottles of Dr. Brown's Cream Soda."
"Sage was a really young, very sensitive, and very talented kid," says Braunstein. "There has been no indication that there was anything wrong in his life."
Not only did Stallone and business partner Bob Murawsky recently sign a new contract acquiring a new film for their company Grindhouse Releasing, but Sage also had intended to marry his longtime girlfriend in Las Vegas this very weekend.
Also, despite some reports that paint Stallone as a recluse, a more accurate description would be that he was a grade-A film geek, known and respected among aficionados of exploitation cinema. Among the movies his company released, in conjunction with Quentin Tarantino, was Gone with the Pope.
'Idolized His Father'"He was a very independent person and spent a lot of time on his own writing and researching and watching movies," Braunstein says of his friend. "He knew everything about movies. The man was a walking encyclopedia of film. It was remarkable, even a little weird how much he knew. He could talk volumes about a movie you had never even known existed."
A rep for Sylvester Stallone, 66, said the Hollywood legend is "devastated and grief-stricken." Sage was the elder Stallone's first-born, with his first wife, Sasha Czack.
Says Braunstein: "He was close to both of his parents and looked up to them."
Indeed, there was a single picture in the room where he was found dead Friday. "It was a picture of Sage at 14 standing next to his dad," says Braunstein. "He idolized his father."