Police in the northern province of Bac Giang told the media Monday that Le Van Luyen, an 18-year-old youth who killed a couple and their daughter at a local gold shop last month, was the sole culprit in the gruesome murder.
Senior Lieutenant-Colonel Le Van Dung of Bac Giang Province Police Department said the conclusion was made based on Luyen's testimony and an examination of the crime scene.
Since his arrest, Luyen's physical and mental health is stable, Dung added.
Luyen previously confessed to the murder and robbery and insisted that he committed them alone.
"His testimony matched closely with what police saw at the crime scene," Dung said.
"There are no traces of a second murderer. Except for blood samples of the victims, the only blood sample belongs to Luyen."
According to Dung, Luyen turned down an offer to choose a lawyer and a guardian during the testimony process and declined to explain why.
He added a lawyer will be appointed to defend Luyen.
A trial for this case will open next month, Dung said.
On August 24, Luyen snuck into the Ngoc Bich Gold Shop (where the family that owned and operated the shop also lived) and killed Trinh Thanh Ngoc and Dinh Thi Chin, the owner couple, and their 18-month-old daughter.
He also cut off the right hand of Trinh Ngoc Bich, the couple's eight-year-old daughter, and slashed her arm and head.
Luyen collected all the gold in the shop, estimated at 1,875 grams in total, (worth US$96,000).
One week later, he was arrested at Na Hinh, a border village near China in the northern province of Lang Son.
Bich, the surviving child, has been discharged from intensive care unit at Hanoi's Viet Duc Hospital.
She is being kept in a separate room until she fully recovers.
After the robbery, Bich underwent surgeries to have her severed hand rejoined and injuries on her brain, head, face and arm treated.
"We are trying to help her rejoined hand move again," said Dr Nguyen Tien Quyet, director of the Viet Duc Hospital.
"Her fingers are nearly okay now, except for the little finger which is a bit weak.
"She can go home in the next 10 days."
Quyet noted that the important thing is to help Bich overcome emotional shock.
"At first, she just wanted to stay in the surgery room. Maybe she was too scared to move to anywhere.
"Her relatives plan to bring her to a relative's house in another province to live for a while following her recovery."