Multiple red flags — including confusion over who was in charge — are to blame in the horrific death of a Brazilian student during a bungee jump-style stunt, according to an expert, who told The Post he saw “pure negligence” on display in the viral video.

Maria Eduarda Rodrigues de Freitas, 21, died when she was hurled off a bridge near Sao Paulo for a rope jump without being attached to a rope on Saturday, plummeting 130 feet to the ground.

Three instructors, Maicon Fernandes Cintra, 42, Luis Felipe Feliciano Egoroff, 32, and Vitor de Freitas Gonçalves, 27, were arrested and charged with homicide on Sunday, after authorities said their business was illegal and unlicensed.

Chris Batten, owner and operator of Bungee Expeditions, told The Post that even before it became clear the rope wasn’t attached, there were other red flags on display.

“What we saw here was pure negligence from many avenues,” he said, adding that for anyone looking at taking part in a rope or bungee jump, there were several key factors to look for.

“I’d say the obvious signs would be, is it run like a business? Is it run like a professional operation? Is there a clear person in charge who is directing other staff?” said Batten, who has more than 30 years of experience bungee jumping.

“There should have been one person in charge who handled everything,” he said.

On Monday, a lawyer for the three suspects said that none of them took responsibility for being in charge.

“If there’s not one person taking charge and then another person acting as backup, that’s a clear red flag,” Batten said.

The instructor added that the directions for each customer should be clear, and that the operation should be “run like a business.”

After a jump, “the next person has already heard and seen that, yet they get the exact same instruction. And that goes for every person,” Batten explained.

“I don’t care if there are 20 people there. The 20th person gets the same instructions as the first person did,” he said.

A crucial red flag in the video for Batten was the apparent lack of backups, which should have been in place even if the rope hadn’t been attached.

A light bungee jumper, weighing between 100 and 150 pounds, would “be on a minimum of three bungee cords, at least in the United States,” Batten said.

In the video of de Freitas, only one or two cords are visible on the ground.

“You get outside of the United States, it’s kind of a wild, wild West out there,” he said, adding that with three cords, they can handle up to 20,000 pounds of weight without breaking.

Describing the video as “unbelievable,” he said he believes it’s gone viral because “it was avoidable. That’s what’s so distressing to all of us, is that there were so many opportunities for that girl to be saved.”

Batten said that visitors must trust their gut before taking part in any extreme sports.

If the operation feels unsafe, or if it gives off a bad vibe, it is always OK to walk away and find a different, safer operator, he explained.

In the US, there is no universal regulator for bungee jumping, which exists in something of a “gray area,” Batten said, meaning it comes down to individual operators’ commitment to safety, training, and detail.

Despite that, Batten, who has taken students on thousands of successful jumps, says the sport is extremely safe.

“One of the things that Americans have always excelled at is taking an idea and making it better. Improving on whatever the design is, making it safe and being able to bring it to the masses,” he explained.