Kim, better known by his stage name Jonghyun, was found unconscious at a rented apartment studio in Cheongdam-dong, southern Seoul, around 6:10 p.m., according to police. Police received a call from his sister around 4:42 pm. that he had sent a text message indicating that he was going to kill himself.
Initial reports revealed that Jonghyun was lying in his room with the coal briquette burning.
SM Entertainment, the company that founded the group, confirmed Kim's death in a statement, writing that his funeral would be "carried out in the quietest manner with his family members and co-workers".
As well as being a singer and an accomplished dancer, he played a large part in the group's songwriting and production, and launched a successful solo career in 2015. He also performed at solo concerts in Seoul last week.
Vikings-Bengals game pits Zimmer v. ex-boss
Minnesota wrapped up the division for just the second time this decade, having also claiming it in 2015. Zimmer left his previous job as the Bengals defensive coordinator to become the Vikings head coach.
A portrait of Kim Jong-hyun, the lead singer of top South Korean boy band SHINee, is seen on an altar during a memorial service for him in Seoul, South Korea, December 19, 2017.
The members of SHINee pose at a press conference in 2014 in Seoul.
Shocked fans have been paying tribute on Twitter.
K-pop's global appeal is such that South Korean President Moon Jae-in used K-Pop celebrities at events, including a state dinner, in China last week in a bid to smooth out a year of hard diplomacy with a star-laden charm offensive.