Phung Van San, 36, residing in Mo Vang commune, was taken into criminal detention on 20/4 by the Lao Cai Provincial Police Investigation Agency. He is being investigated for intentionally causing injury resulting in death.

San confessed to police details of the fatal beating. He admitted to using an electric cord to strike his 12-year-old son's back and legs on the night of 9/4. He forced the boy to stand in the middle of the house until 3:30 h on 10/4 before allowing him to sleep.

The next morning, San discovered his son dead and continued his routine. Around 5 h that same morning, San woke up and went to cut grass on the hill as usual. Returning home at midday, he found his son lying motionless on a chair, already deceased. San then went back to work until about 17 h.

Later that evening, San buried the body. At 19 h, San used his motorbike to transport the body from their home. He buried it on the family's cinnamon hill in the Tung Chieu ravine, Thac Tien hamlet, Mo Vang commune, about 3 km away.

The disappearance of the boy was reported to authorities days later. On 13/4, the Mo Vang Semi-Boarding Ethnic Minority Secondary School reported to the police that the 6th grade boy had been absent for several days.

Initial inquiries were met with false information from the family. Mo Vang commune police questioned San and the boy's grandmother. Both claimed the boy had left home on 9/4 and had not returned, stating they had searched for him but found no trace.

Authorities grew suspicious due to San's behavior, leading to the confession. Simultaneously, officials noticed San exhibited signs of distress and frequently visited the hill. He was summoned for questioning, which led to the uncovering of the incident.