A Hawaii crime boss who died in federal custody this month was killed by an opioid overdose, the Honolulu medical examiner said Tuesday.
Michael Miske, 50, died of “fentanyl and para-fluorfentanil toxicity,” the coroner's office said in a statement.
She added that the death appears to have been accidental, but the case is still under investigation and the autopsy report will likely take at least another 30 days.
It is not clear how Miske obtained fentanyl or para-fluorofentanyl while at the Federal Detention Center in Honolulu.
Para-fluorofentanyl is a synthetic opioid that appears in illicit drugs and is more powerful than fentanyl.
The Bureau of Prisons did not immediately respond to an email seeking comment.
Miske was found unresponsive in custody on December 1.
The efforts of staff and emergency medical responders were unsuccessful in saving him, the agency said.
He was convicted in July of 13 charges, including racketeering conspiracy, murder in aid of racketeering and kidnapping resulting in death.
He was accused of orchestrating crimes that included kidnapping a 72-year-old accountant he was in debt to, releasing a toxic chemical into the nightclubs of a rival, and killing his late son's best friend.
The conviction gives the government control of up to $28 million of Miske's assets, including boats, homes and artwork.
He was scheduled to be sentenced on January 30.
The Bureau of Prisons operates 122 federal prisons across the country.
It has suffered a series of incidents and crises in recent years, from rampant sexual assaults and other criminal misconduct by staff, to chronic understaffing, runaways, and celebrity deaths.
In August, an inmate and two other people were charged with conspiring to mail drugs to a California prison, where a mailroom supervisor died after opening a letter that prosecutors said was filled with fentanyl and other substances.
