Saturday night at a club blurred into Sunday morning when a man passed around a knife tipped with drugs in a Pittsburgh apartment, offering a bump to the men gathered for the after-party.

By sunrise, three men were dead and four others hospitalized after overdosing on a drug that investigators believe could be fentanyl, court documents said.

Authorities arrested Peter Rene Sanchez Montalvo early Tuesday morning in McKees Rocks, west of Pittsburgh, and he has been charged with “illegal distribution of a controlled substance resulting in death and serious bodily injury,” officials said. It is unclear whether Sanchez Montalvo, also known as Carlos, has an attorney.

His arrest ended a frantic 24-hour search for answers after police initially reported that all men involved wore orange wristbands, fueling speculation and fear that they took drugs circulated at a nightclub and that there could be more deaths. Authorities later clarified that the danger was from drugs consumed only at the apartment.

In court documents, an FBI agent re-created the night during which a group of men at the Insomnia Discotec, a club in the Brookline neighborhood popular with the Hispanic community, offered a band there money to play at an after-party in an apartment on the city’s south side, nestled into the Monongahela River.

A witness told investigators that Sanchez Montalvo cut into a kilo of narcotics that the partygoers believed was cocaine. He then offered the men gathered in the apartment a sniff straight from the knife, which several did, according to a video shared with the FBI.

People immediately began to “drop” and suffer adverse affects, survivors told investigators.

At about 4 a.m. on Sunday, police and paramedics responded to a call about an unresponsive man found in an elevator. Rubiel Clemente-Martinez, 32, of Columbus, Ohio, was found dead. Police tracked his activity to apartment 421, where they found five other men.

Josue Soberal Serrano, 38, of Carthage, Mo., and Joel Pecina, 32, of Coraopolis, Pa., were found dead inside, authorities said, and three others were in various states of medical emergency. Another victim was found alive in a street nearby, authorities said.

Police interviewed the person who rented the apartment, who said he was paid $500 to turn over the keys to Sanchez Montalvo for his use. Renting apartments under someone else’s name is a common strategy for drug traffickers to avoid law enforcement detection, court documents said.

Investigators believe the drug is fentanyl or a fentanyl analog but said the Allegheny County Medical Examiner’s Office would make that determination.

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