A migrant from Guatemala has been arrested after allegedly setting a sleeping subway rider on fire in Brooklyn early Sunday morning, then watching as the victim tragically burned to death in what the police commissioner described as "one of the most depraved crimes one person could possibly commit."

The horrific incident occurred around 7:30 a.m. aboard a stationary F train at the Coney Island-Stillwell Avenue station. The brutal crime stunned commuters, MTA personnel, and NYPD Commissioner Jessica Tisch, who stated that the senseless act "took the life of an innocent New Yorker."

"As the train pulled into the station, the suspect calmly walked up to the victim, who was in a seated position at the end of a subway car ... and used what we believe to be a lighter to ignite the victim's clothing, which became fully engulfed in a matter of seconds," Tisch explained at a press briefing.

Officers on patrol noticed both the smoke and the distinct odor, leading them to the victim engulfed in flames, according to the commissioner.

They managed to extinguish the fire, but tragically, the victim succumbed to her injuries at the scene.

Authorities identified the 33-year-old suspect as having arrived in the United States in 2018 from Guatemala. His legal status was not immediately clarified on Sunday evening.

Disturbing footage obtained by The Post captured the suspect calmly watching the flames consume the still-unidentified woman, who had been standing near the open subway door.

A transit officer walked by and appeared to radio in a message, continuing down the platform.

After the officer passed, the suspect stood as if to leave, and the video abruptly ended.

In another video, police officers were heard calling out to the onlookers, "Did anybody see anything? Did anybody see anything?" as smoke billowed from inside the subway car.

The suspect boldly remained seated on a nearby bench while officers gathered around him. At one point, he pulled his hood over his head before one officer addressed him.

"Do me a favor? Walk down there," the officer instructed, pointing down the platform. "I need this space cleared up."

The man then stood up and exited the scene.

Tisch stated, "Unbeknownst to the officers who responded, the suspect had stayed on the scene and was seated on a bench on the platform just outside the train car."

"The body-worn cameras on the responding officers produced a very clear, detailed look at the killer," she added.

Later that day, three high school students contacted police, reporting that they had seen the man, whose image had been released by the NYPD, at the Jay and York Street station on the F line, according to Tisch and NYPD Chief of Transit Joseph Gulotta.

When transit officers arrived, they found the suspect already on another train leaving the station, still dressed in the same gray hoodie, wool hat, and paint-splattered pants he wore during the attack.

Officers coordinated with transit personnel to halt the train at Herald Square, where they conducted a search from car to car until they located and arrested the suspect.

Tisch confirmed that the suspect was found with a lighter in his pocket when taken into custody.

"I want to thank the young people who called 911 to help," Tisch said. "They saw something, and they said something, and they did something."

Gulotta praised their actions, calling the arrest "amazing work done by the public and the police working together."

Authorities do not believe the suspect and the victim were acquainted prior to the incident, Gulotta added.

Earlier, investigators, including police officers, firefighters, and medical examiners, meticulously searched the tracks for evidence after the area was cordoned off.

Around 1 p.m., officials removed a body bag containing the woman's remains from the train, transferred it onto a gurney, and then wheeled it to a medical examiner's van.