MIXNINE star Kim Dong Yoon has passed away at the age of 20.
The Spectrum band members death was confirmed by his agency, WYNN Entertainment.
The agency said: The bereaved family, Spectrum members, and WYNN Entertainment family are all grieving the deceased, who so suddenly passed.
The funeral will be held quietly according to the will of the bereaved family.
No details of Dongyoons cause of death have been revealed.
Dongyoon was the main rapper of group Spectrum, with the band debuting on 10 May this year.
He only turned 20 last month, on 3 June.
Spectrum consists of Minjae, Dongkyu, Jaehan, Hwarang, Villain, Eunjun, and the late Dongyoon.
A fan profile on the band said that Dongyoons hobbies were eating at good restaurants, woodworking and creating things, while he hated dieting, washing dishes, and food being taken from him.
It also said that his motto was lets do it until its impossible.
Dongyoon was eliminated in episode 13 of MIXNINE, narrowly missing the final in January this year.
Spectrum fans and K-pop lovers in general took to Twitter to share their condolences and shock at Dongyoons passing, as well as offering to support any Spectrum stans.