The Bee reported that the first two responding officers were also taken to the hospital when they began feeling ill, potentially side effects of being exposed to fentanyl in the house.
"We were waiting and have been waiting, unfortunately, for this to happen in the sense that we knew fentanyl had been moving west and in other parts of the country they're really seeing the greatest impact of this drug", O'Brien said.
While the substance that caused the overdose has not been tested, O'Brien said, "We have every indication that this mass overdose incident was caused from the ingestion of some form of fentanyl in combination with some other substance".
Police did not provide many details of the person who died, but said he was an adult male who died on the scene.
According to O'Brien, eight people were admitted, four of whom are listed as being in critical condition. The drug has been blamed for a wave of overdose deaths across the nation. He described seeing six people undergoing CPR at the same time. That home is now being treated as a haz mat site and no one is being allowed to enter without proper precautions.More news: House GOP leader vows action against King over race remarks
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They were treated for exposure to fentanyl or a fentanyl-like substance while they were helping the victims.
Fentanyl, a synthetic opioid pain reliever, is 50 to 100 times more potent than morphine.
The police chief said officers administered CPR and six doses of Naloxone - a treatment for opioid overdoses used as a nasal spray or an injection.
"That is changing, unfortunately", He said, "and now we've had this mass casualty incident ... likely to have been caused by fentanyl". O'Brien said a narcotics task force was trying to determine the source of the drugs.