After the 15-year-old girl went missing on Monday morning in Petaling Jaya, Malaysia, her family began a frantic search for her.
Ng Yuk Tim had met with friends for breakfast that day and then met a 23-year-old friend to discuss costumes for an upcoming Cosplay event.
The friend initially said he had dropped her off at the Kelana Jaya LRT station in Petaling Jaya that afternoon.
But she didn't even leave his home, The Star reported.
He had allegedly hit her with a dumbbell, killing her on the spot. He then allegedly stuffed the body in a green suitcase and dumped it in Shah Alam.
Yuk Tim's body was found in a green suitcase on Tuesday, clad in a T-shirt and underwear.
Selangor deputy police chief Deputy Comm Datuk Abdul Rahim Jaafar said late on Wednesday that a post-mortem showed that she died of severe head injuries due to three heavy blows to the head.
Mr Kuan Chee Hong, a community crime watcher, told reporters that he had repeatedly questioned the man on what happened to the girl before he got the confession.
He handed the suspect to the Petaling Jaya police on Tuesday night. Mr Kuan said he had met Yuk Tim's mother, Ms Sim Yee Ling, 35, at a restaurant after she asked him to help her find her daughter.
He told The Star: "When I arrived, the suspect was also there with her.
"I noticed he had bite marks on his left hand. So I asked him if he had anything to do with Yuk Tim's disappearance as he was the last person to have seen her."