The bass player had also been suffering from heart disease
Slipknot‘s Paul Gray‘s death has been ruled an overdose.
The bassist, who passed away last month, was the victim of a lethal combination of morphine and the narcotic painkiller fentanyl – both injectable substances.
According to E! Online, Polk County Medical Examiner Dr Gregory Schmunk issued the death certificate on Friday (June 18).
Schmunk also confirmed that Gray had been suffering from heart disease.
Investigators have not found evidence that Gray had a prescription for either substance, and police officials have said that it is possible charges could be filed in the case at some point in the future.
A hypodermic needle and pills were found near his body in his hotel room in Des Moines, Iowa, but the coroner determined that the pills did not contribute to his death.