The B.C. Coroners Service says the death of the only inmate convicted of murder following the 1971 Attica, New York, prison uprising was an accident caused by alcohol and cocaine use.

The body of 61-year-old John Boncore was found March 13 in his home on the Adams Lake Indian Reserve, near Chase, B.C.

The coroner's office said Monday Boncore had an enlarged heart, had recently used cocaine and had a potentially life-threatening blood alcohol level of more than 0.35 per cent when he died.

Boncore, also known as Splitting the Sky or by the name Dacajeweiah, was a member of the Mohawk First Nation and was born in Buffalo.

He was known as John B. Hill at the western New York maximum-security prison where 32 inmates and 11 civilian employees died during a five-day siege in 1971.

Boncore was convicted of fatally beating William Quinn, a guard at the prison, but received clemency and was pardoned after a year, in 1976.

Boncore made headlines in 2009 in Alberta when he tried to make a "citizen's arrest" of former President George W. Bush for alleged war crimes.

With files from CBC News