The actor acquired the medications through "doctor-shopping," in which he visited seven different doctors and seven pharmacies, using an alias on at least one occasion, Brown said. The drugs included Valium, Vicodin, Xanax and Soma.
The doctors did not appear to know that Haim was using multiple sources for the medication, said Brown, who called the '80s film star a "poster child" for prescription drug abuse. Investigators have also found that thousands of pills were obtained in Haim's name before this year.
Last month, investigators linked Haim to a massive illegal prescription drug ring.
Haim died on March 10 at the age of 38. The coroner has not yet released an official cause of death, but the Lost Boys actor's mother has said her son died of an enlarged heart and that he had fluid in his lungs.