A man killed his twin brother and 7-year-old nephew before surrendering to police in Hongkou district over the weekend, local media reported.

The victims, a man in his 40s and his 7-year-old son, were found dead at their home on Shajinggang Road around 3 pm, according to a report in the Xinmin Evening News. Neither the victims nor the suspect was identified.

Police detectives cordoned off the victims' home to conduct their investigation, the report said. The victims had obvious knife wounds on their bodies. 

The suspect, who was the elder twin, walked out of his brother's home Saturday and told neighbors that he had just killed several people.

The frightened neighbors immediately called the police. The victim's wife was not at home at the time.

She learned about her husband and son's deaths later from police.

Neighbors told police that the suspect appeared to be mentally unstable. Police said he would undergo a psychiatric evaluation.

The case remained under investigation Sunday.