Kim Jong-hyun, lead singer of the K-pop boy band SHINee, died on Monday, Dec. 18 in what police are calling a suicide. He was 27.

Jonghyun made his debut as SHINee's lead singer under the SM Entertainment banned in May 2008. He enjoyed a successful career not only in group activities but also as a solo singer and songwriter.

The singer's death is a huge shock as it comes just days after he wrapped up solo concerts on Dec. 9 and 10.

Cause Of Death

The South Korean superstar was found in an unconscious state in his residential hotel in Seoul's Gangnam District and immediately rushed to a nearby hospital.

He was admitted to the hospital in a state of cardiac arrest but all attempts to revive him were unsuccessful. The singer was later pronounced dead.

Authorities found lit coal briquettes on a frying pan in the room where Jonghyun was found. Burning coal briquettes in a closed room lead to carbon monoxide poisoning. It is a common method used to commit suicide in Korea, which has one of the highest suicide rates in the world.

Sister Confirms Suicide

Before he was discovered, Jonghyun's sister alerted authorities as she feared for her brother's life after he sent her a text message alluding to a "final farewell."

"It's been really hard for me until now, " the message read. "Please let me go and tell me I've worked hard, last good bye."

The message led Jonghyun's sister to believe he was about to commit suicide and prompted her to call emergency services.

Record Label Releases Statement

Fans of the South Korean superstar were left devastated after SM Entertainment, the record label that manages the 5-member band, confirmed Jonghyun's death on Monday.

"We are sorry to deliver such heartbreaking and unfortunate news," the official statement read. "On December 18, Shinee member Jonghyun suddenly left us "Jonghyun was the best artist who loved music more than anyone and gave his all on the stage," the statement said. "It is heartbreaking to deliver such sad news to the fans who loved him."

The '27 Club'

Jonghyun is the latest celebrity to join the "27 Club," which comprises of a group of young celebrities who died at the age of 27. The club includes the likes of Kurt Cobain, Jimi Hendrix, Jim Morrison, Amy Winehouse as well as Star Trek actor Anton Yelchin.