The bassist for US metal bank Slipknot died last month of an accidental overdose, an autopsy has revealed.
Toxicology tests showed a fatal level of morphine and fentanyl, a synthetic morphine substitute, in his blood. Police said there was no evidence of a prescription for either drug.
His body was found by an employee at a hotel Des Moines, Iowa on 24 May.
The autopsy also revealed signs of significant heart disease, police in Urbandale, a Des Moines suburb, said.
A spokesman for the Urbandale police said they were trying to find out how Gray obtained the drugs.
The spokesman said charges were possible.
