Stephan Bonnar’s sudden passing late last year came as a shock to many MMA fans. The longtime UFC veteran had had his share of struggles outside the cage, but at just 45-years-old, his death was sudden and unexpected.

At the time, the UFC reported that the Hall of Fame inductee had died “from presumed heart complications while at work.” No further updates or statements were given, beyond confirmation of his death.

According to a report issued by the coroner's office in Clark County, Nevada, Stephan Bonnar died as a result of an unintended drug overdose. The coroner's findings specifically blame fentanyl, parafluorofentanyl, and mitragynine for the his demise.

 Two of the three compounds are exceedingly potent opioids, including the strong synthetic opioid fentanyl and the highly potent opioid equivalent parafluorofentanyl. Mitragynine, the third component, is an alkaloid that aids in mediating opioid receptors. The three drugs are all used to treat pain.

Prior to his passing, Bonnar was a well-known user of opiod painkillers to manage his painful injuries from his demanding years as a professional wrestler and mixed martial artist. Unfortunately, Bonnar was never able to get past the horrible pain he endured.

'The American Psycho' is one of the most important people in the history of the promotion, despite the fact that he never claimed a UFC title.

He competed in the inaugural season of The Ultimate Fighter and lost to eventual 205-pound champion Forrest Griffin in one of the most significant fights in UFC history. He competed against famous fighters like Rashad Evans, Jon Jones, and Anderson Silva.