The fighter spent five days in a Florida hospital and for two of those he was brain dead, says Dr Craig Mallak, chief medical examiner for Broward Country.
Officers investigating a call of a possible drug overdose found Josh Samman unresponsive but with a pulse on Thursday night, according to a report issued by the Hollywood Police Department.
Troy Kirkingburg, a friend and an MMA announcer, was pronounced dead at the scene.
A friend of the pair found them and called emergency services. Josh Samman started his professional MMA career in 2007 before being featured on reality show The Ultimate Fighter in 2013.
He then moved to UFC with three straight stoppage victories, including a debut knockout of Kevin Casey, Muhammad Ali's son-in-law. But he lost his last two fights.
In addition to his UFC career, Josh Samman also self-published an autobiography and wrote for MMA and UFC news outlets. He spoke openly about the sport's drug policy and his own issues with substance abuse.