Sage Stallone Laid to Rest
07/21/2012 AT 06:00 PM EDT
The 36-year-old son of Sylvester Stallone was found dead in his San Fernando Valley home July 13.
Sage, who acted with his father in 1990's Rocky V and 1996's Daylight, also wrote and directed the 2006 short film Vic.
The cause of death remains unknown pending the results of toxicology tests, which usually takes weeks.
Some reports suggested Sage may have overdosed on prescription drugs, and longtime friends of Sage's tell PEOPLE that he did take prescription pills regularly for anxiety and other issues. But his friend and lawyer, George Braunstein, said Sage never showed any signs of drug use or addiction, and didn't even drink.