On Monday night, Lisa Oliphant saw her 15-year-old nephew running down the street.

The teen, Robert Seals, was on fire.

"You could see his eyelashes and everything just burning," Oliphant told the Orlando Sentinel. "And his hair, and his chest burning. He put himself out in the front, the back of his shirt was still burning."

According to authorities, Seals would later tell investigators that that blaze was a "fire challenge," a type of social media stunt in which participants cover themselves in rubbing alcohol and then set it on fire.

The teenager "willingly and voluntarily" took part in the stunt, the Orange County Sheriff's Office said in a press release.

"Both victim and witness statements indicate the victim asked one of his friends to ignite the rubbing alcohol," the release stated.

A sheriff's spokeswoman said in an email Thursday that the incident, which also involved a 12-year-old and another 15-year-old, was not captured on video.

Seals' family, however, seemed to push back on the official account.

"He ain't doing ... stupid stuff like that," Oliphant said, according to Orlando Sentinel.

Oliphant told the newspaper that her nephew plays football and practices mixed martial arts. The teen, who lives with her, wouldn't do such a thing, she said.

Authorities were investigating Monday's fire, the sheriff's office said.

"The OCSO is exploring the possibility of culpable negligence charges against the two other juveniles involved," the sheriff's office news release stated. "However, the case will be ultimately forwarded to the State Attorney's Office for further review."

Seals, who suffered burns on his arms and back, was airlifted to a hospital, according to WFTV, an ABC affiliate in Orlando. His condition was unclear Thursday.

"His neck ... swelled up so bad," Oliphant told the Orlando Sentinel. "My nephew is permanently damaged and that boy did bodily harm to my nephew. I want something done about it."

The fire challenge is not a new phenomenon. A Kentucky teenager made headlines in the summer of 2014 after he suffered second-degree burns while imitating the fire challenges he'd seen online.

Why, precisely, would you do such a thing?

"I don't know; I wasn't thinking really," the teen told WKYT-TV. He said that the one thing the videos never showed was the end, when the blistering begins.

"What they don't show at the end of the videos is the consequences of doing this, getting second- and third-degree burns," Lexington Fire Department Captain Chris Harrod told WKYT at the time.

As The Washington Post's Caitlin Dewey explained last year: "The thing is, it is a trend - and the overwhelming forces of peer pressure and desire to belong will compel many teens to keep following it, regardless of the (very obvious) risks."