A high school student was found dead on a hill in Bundang in Gyeonggi Province, Monday morning, six days after he went missing on June 22.

Police suspect that Kim Hwi-seong, 18, took his own life. He was found lying down with a plastic bag over his head, and there were no signs of external injuries.

Police suspect that he suffocated to death, but said they will determine the exact cause of death after an autopsy by the National Forensic Service, upon the agreement of his family.

Kim, a senior at Seohyun High School, went missing after he sent a text message to his aunt on June 22 saying that he would be home around 9 p.m. after studying at school.

He left his phone in the desk drawer in his classroom and stopped by a convenience store near the school about 10 minutes after he sent the message at 4:40 p.m.

Security camera footage showed that he added credit to his public transportation card and bought a standard plastic garbage bag at the convenience store.

Then he bought study guide books from a bookstore near Seohyeon Station at 5:22 p.m., and was last seen on an elevator that goes down an overpass at 5:28 p.m., security camera footage showed.

The bus that he took did not have a black box camera for the interior of the bus, but based on an analysis of recordings on other buses that passed the bus stop at the time, police determined the bus he took.

Police believe he paid cash for the bus ride and alighted at the Korea Saemaul Undong Academy in Bundang, the last stop of the bus.

Bundang Police Station said Monday they found Kim’s body near a footpath on a hill near the main entrance of the Saemaul academy at 6:33 a.m.

Police had been searching for Kim since Wednesday. On Sunday, they mobilized about 180 personnel, a helicopter, drones and search dogs for the effort.

Kim’s parents had flyers posted all around Bundang asking for help from anyone who may have seen their son since June 22.

Police found no traces of Kim being involved in any school violence. No note has been found.

A family member told police that Kim was scolded by his father over his future the day before he went missing, but his family said the high school senior got along well with his family and often discussed his future with them.

News about Kim comes just two months after medical school student Sohn Jung-min was found dead in the Han River on April 30, six days after he went missing.

Last year, police received a total of 67,612 missing reports of persons aged 18 or older. Of them, 1,710 were found dead, and 925 have not been found yet.