A high school student found on fire in the parking lot of Academic Magnet High School on Wednesday morning had soaked his clothing with an accelerant and set himself ablaze to commit suicide, police said on Friday.

Aaron Williams, 16, died on Thursday at a Georgia burn center. Capt. Scott Deckard of the North Charleston Police Department said the boy had left a suicide note, and an investigation into his death will determine which accelerant he used to ignite his clothing.

"We have never seen anything like this, not that there has never been an incident like this," Capt. Deckard said. "I think that's why it's carrying so much weight."

Anja Evenson told a local television station she saw black smoke from the window of her classroom at Charleston County School of the Arts, which is next door to Academic Magnet School where the incident took place.

"He was just completely black and there was black smoke coming from him and he was just walking around ... on fire," she said. "I started shaking tremendously. I've never felt such terror inside me."

A parent who was in the school's parking lot at about 8:20 a.m. also witnessed the boy engulfed in flames, police said.

According to the 911 call from the school, witnesses saw the burning boy running toward the school's entrance, and students and teachers rushed out with fire extinguishers. They put the fire out and covered Williams with a blanket until police and EMS arrived.

Academic Magnet High School serves about 600 students with admission based on academic eligibility. This year, it was ranked among America's best high schools by Newsweek magazine.