South Korean K-Pop boy band SHINee’s lead singer Jonghyun died early Monday. Jonghyun, whose full name is Kim Jong-hyun, was found unconscious at a rented studio apartment in capital Seoul, and was later declared dead at a hospital.

The 27-year-old's sister told police that she thought Jonghyun may have attempted suicide. Police launched an investigation into his death and an autopsy is pending. According to local media reports, police said the singer was found with a burning coal briquette nearby.

"On Dec. 18, 2017 at 4:42 PM (local time) Jonghyun's older sister reported to police that her brother was about to commit suicide," Gangnam Police said in a statement.

"We went to his residence in Chungdam and discovered that he had attempted to commit suicide with brown coal briquettes lit inside a frying pan."

"Emergency responders were with us at the time so we rushed him to the Konkuk University Hospital in a state of cardiac arrest," the statement added.

According to the Mirror U.K., Jonghyun's cause of death is said to be carbon monoxide poisoning, which could have been caused by breathing in fumes from the lit coal briquettes.

Social media users reacted with shock after learning about Jonghyun's untimely death and tributes poured in.

"Jonghyun is a beautiful person and artist who touched lives. He will always be with us through his music," one user wrote, while another said: "Jonghyun suffered in silence for so long. if he only knew how greatful i am that he existed. a big thank you to him for pouring his heart out all along this path."

"I can't even imagine what happened to Jonghyun, this is a lesson for all the companies, they need to pay attention to their artists who are suffering from depression and they should prioritize their artist's health first becoz that is the most important," another user wrote.

Born on April 8, 1990, Jonghyun began his career in 2008. He participated in S.M. Entertainment's project group S.M. The Ballad. Jonghyun debuted as a solo artist on Jan. 12, 2015, with his first EP, titled "Base." The same year, Jonghyun released a compilation album, "Story Op.1." On May 24, 2016, Jonghyun released his first studio album, "She Is," followed by his second compilation album, "Story Op.2" on April 24, 2017. In 2016, he won the Golden Disk Awards for "Base."