Kim Jonghyun, the lead singer of K-Pop outfit SHINee, was found dead on Monday evening. He was 27.

Kim, known better to fans as simply Jonghyun, was found unconscious in the Seoul apartment. Kim was taken to a hospital, but Korean news agency Yonhap reports that he never regained consciousness (via Variety).

Kim’s body was discovered in the Gangnam district’s Cheongdam quarter after his older sister reported to police that Kim was behaving erratically.

Seven local news outlets reported that Kim committed suicide, though the outlets did not name their sources. Other outlets say that Kim died of carbon monoxide poisoning from heating up charcoal inside his apartment.

The local police stated in a briefing that Kim sent a text message to his sister that sounded like a suicide note. The message reads, “I’ve had a hard time. Please let me go and say that I did a good job. This is my last word.”

SM Entertainment, the management group that represents Kim, has yet to offer a statement.

Korean celebrity culture is particularly intense. Performers are often both strictly managed by their agencies and held to incredibly high standards of conduct and behavior by their fans and the public at large. A single social misstep can lead to an entire segment of a performer’s audience turning against a celebrity.

SHINee is a five-piece boy band that was originally formed in 2008 by SM Entertainment. SHINee gained a reputation for being among the most skilled performers in their field and became highly influential in Korean pop culture.

SHINee released six albums in Korea and five for Japanese audiences, with its latest Japanese album, Five, being released in February 2017. The group then embarked on a world tour spanning 10 cities and 25 concerts.

SHINee also made two film appearances. The group was featured in I AM in 2012 and the documentary SMTown: The Stage in 2015. The group also appeared on several television shows and were named honorary ambassadors of Gangnam in 2013.