CHICAGO (CBS) — An autopsy performed on Chicago rapper Juice WRLD on Monday was inconclusive, as authorities await additional tests to determine how he died.

Juice WRLD, whose real name was Jarad Higgins, died at Midway International Airport on Sunday after suffering a seizure, after arriving on a private flight from California.

A Homeland Security officer at the airport administered Narcan, but he later died at Advocate Christ Medical Center in Oak Lawn according to police and the Cook County Medical Examiner’s office.

“After arriving in Chicago, Mr. Higgins suffered what appears to be a medical emergency with no obvious signs of foul play,” police spokesman Anthony Guglielmi tweeted. “Individuals aboard the aircraft are cooperating.”

The Cook County Medical Examiner’s office conducted an autopsy on Monday, but was unable to determine a cause of death, pending further studies – including additional examinations of his cardiovascular and nervous systems, tissue studies, and toxicology tests.

Area Central detectives were conducting a death investigation.

Meantime, the music world and Higgins’ hometown are mourning his passing.

Born in Chicago, Higgins moved to south suburban Homewood as a child, and graduated from Homewood-Flossmoor High School in 2017.

He became a breakout rap star in 2018, when his debut album “Goodbye & Good Riddance” reached No. 6 on the Billboard 200 chart in its third week of release in June 2018. His second album, “Death Race for Love,” debuted at No. 1 on the Billboard 2000 in March 2019.

Juice WRLD also won the award for Best New Artist this year at the Billboard Music Awards.

As CBS 2’s Mike Puccinelli reported, Juice WRLD’s track “Lucid Dreams (Forget Me)” has been streamed a billion times and first put the rapper on the map.

But long before hundreds of millions of people were listening on YouTube, Donielle Davenport was listening as an audience of one.

“It’s a little mindblowing that I would listen to it in his headphones,” Davenport said.

That’s because Davenport was the young rapper’s chemistry teacher at Homewood-Flossmoor High School. Juice WRLD is a Chicago native, but moved to south suburban Homewood as a child. He graduated from Homewood-Flossmoor in 2017.

Teachers and staff described him as a brilliant, talented, and creative student.

Davenport said she’d catch Juice WRLD writing songs when she wanted him to be working on chemical equations.

“I would tell him, you know, ‘Hey Jarad, just finish your work first and then we can talk about music,’” she said.

Davenport said Juice WRLD was “just really fun to be around.” That was exemplified, she said, when he and a buddy decided to take her camera and fill it up with pictures of themselves.

“I really do love all of my students,” she said. “But he held a special place.”

And upon news that Juice WRLD had died after landing a private plane at Midway, Davenport had an immediate involuntary reaction.

“I just started crying. I mean, there’s really other reaction I could have had,” she said.

And it brought her back to her classroom at Homewood-Flossmoor when she posed with Jarad and a couple of friends.

“It just took a little bit to process like, wow, like, he’s gone,” Davenport said.

Former classmate Tristan Kenady, now a senior at Homewood-Flossmoor, met Higgins during Kenady’s freshman year. He said Higgins would always freestyle in the hallway and lunchroom.

“I never knew someone who could freestyle like that. Not even my favorite rapper could freestyle like that, but he was a different breed,” he said. “I never knew that as soon as he left HF he was just going to blow up like that. That was all unexpected to me.”

Other students, like Kalel Fargo, didn’t know Higgins personally, but said his music is inspiring.

“I’ve always wanted to meet him, but now I just can’t do that anymore, but he’s in a better place,” Fargo said.

Juice WRLD was open in his songs and in his words about drug use in the music business. But earlier this year, he told his million Twitter followers that he was done with codeine saying, “Addiction kills all, but you can overcome.”

Davenport says she had hoped to see Jarad again, but now must come to grips that as he all too prophetically sang.

“What’s the 27 club?” he intoned in his track “Legends.” “We ain’t making it past 21.”

And he lived less than a week after turning 21. But Ms. Davenport finds comfort in the fact that he lived out his dream.

“He was like, you know, ‘Miss D, when I make it, I’m going to buy you a Lamborghini!’” she said.

Ellie Goulding, who collaborated with Juice WRLD on the song “Hate Me,” recalled him as “such a sweet soul” in a post on Twitter.

Chance the Rapper also issued a tweet characterizing Juice WRLD as a “young legend.”

Juice WRLD’s label, Interscope Records, also released a statement on Twitter Sunday night honoring eth rapper for making “a profound impact on the world in such a short period of time.”

(© Copyright 2019 CBS Broadcasting Inc. All Rights Reserved. The Associated Press contributed to this report.)