Seven people have been arrested for allegedly selling fentanyl marketed as heroin after video captured one of their customers overdosing at an open-air drug market on a Bronx street corner, according to an indictment filed Thursday.

The arrests follow a six-month investigation involving the NYPD, DEA and Bronx DA. Four men and three women face an array of drugs and weapons charges in the scheme to sell heroin and fentanyl at the drug market just a few blocks from Fordham University.

The drugs, stamped with an image of a kneeling skeleton and the brand name “Pray for Death,” were sold near a recycling collection site so customers could return empty cans and bottles to get cash for the drugs, authorities allege.

The area in and around the drug market, at Marion Avenue and 194th Street in Fordham, has some of the highest overdose rates in the city, according to officials.

Authorities say 39-year-old Billy Perez was the head of the supply chain. They allege he supplied fentanyl and heroin to an intermediary, who passed them along to 61-year-old Hector Figueroa, who then handed them off to street-level dealers who operated at the drug market.

“This predatory organization was set up for business at a recycling collection site where potential customers would return empty cans and bottles to scrape together the cash to purchase dime bags of what they thought was heroin,” said Special Narcotics Prosecutor Bridget Brennan.

During the investigation, 35-year-old Stanley Sacarillo allegedly made more than a dozen sales to undercover officers, including the largest sale — 300 individual glassines of purported heroin for $2,850. An analysis by the NYPD found the glassines to contain fentanyl, not heroin, authorities say.

According to the indictment, video captured Sacarillo selling glassines of narcotics to a customer at the drug market. The customer snorted one envelop and then another before overdosing. Sacarillo called 911 and carried the customer around a corner, where he was revived by first responders, authorities say.

During a search of Perez’s apartment Wednesday, Police found $200,000 in cash and 215 glassine envelopes of heroin and fentanyl, according to authorities, who say another 100 glassines of suspected heroin and fentanyl were found at Figueroa’s residence, around the corner from the drug market.

The seven defendants face charges that include conspiracy, criminal sale and possession of a controlled substance, criminal possession of a weapon, attempted criminal possession of a weapon and reckless endangerment.

The charges stem from 15 alleged sales of drugs to undercover officers worth nearly $10,000. The indictment says the defendants claimed the drugs were heroin but that laboratory analysis found them to be either a mixture of heroin and fentanyl or in some cases fentanyl alone.

Fentanyl is 50 times stronger than heroin, according to the city health department.

New York City experienced a 46 percent increase in overdose deaths in 2016, which the health department attributes to fentanyl.