The four were not linked by their age, occupation or residence.

Their ages varied from 26 to 44, and each were from Jecheon, Seongnam, Yangju and Incheon city.

The police found them as they were tracking a missing-person report filed from Jecheon, North Chungcheong Province.

The family of the female victim reported their daughter missing “after going to Seoul to look for a job” on Friday.

The police followed the reported victim’s trail and discovered she had dined with three strangers at a restaurant before disappearing into the office building.

The other three had been reported as missing in their respective residential areas.

The police presume the four met through an online suicide community.

If found, operators of such a community will be held legally responsible for encouraging the suicide or knowingly failing to prevent it.

The police later discovered a four-page letter of apology addressed to family in the pocket of the 34-year-old deceased.

He had been the one who borrowed the office space from an acquaintance.

The police also learnt that on Aug 22, three of the deceased, with a different fourth member, were found to have attempted suicide at a studio apartment in Incheon.

Their reasons for attempted suicide then had been financial difficulties and health problems.

By Lim Jeong-yeo (kaylalim@heraldcorp.com)