An uncle of Cho made the report to police, saying he could not reach his family. Police officers who were called to the scene unlocked the door and found the victims.

All the victims' bodies except Shin's ex-girlfriend were found covered with plastic and a large washbasin. Cho was found lying in the living room with signs of severe beating and ligature marks around her neck that suggested strangulation. Shin was discovered in another room.

Police have secured surveillance footage of Shin entering the apartment. He was wearing a hat and sunglasses and was seen carrying a bag that police believe likely had the murder weapons inside.

Police believe he used a taser gun to subdue the victims.

Shin and Cho had been living together for about a year until the relationship ended in August, police said. The victims'

families and friends told police that they remember the Chos once introducing Shin to them as their "son-in-law."

Police plan to ask the crime lab to perform autopsies of the victims, while investigating the case to establish a motive. (Yonhap)