(Associated Press) Aaron Francisco Chavez swallowed at least one of the sky blue pills at a Halloween party before falling asleep forever.

He became yet another victim killed by a flood of illicit fentanyl smuggled from Mexico into the Southwest -- a profitable new business for drug gangs that has pushed the synthetic opioid to the top spot for fatal U.S. overdoses.

Three others at the party in Tucson also took the pills nicknamed "Mexican oxy" and police flagged down by partygoers saved them by administering naloxone overdose reversal medication. But the treatment came too late for Chavez, who died at age 19.

The four thought they were taking oxycodone, a much less powerful opioid, investigators believe.

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