The doorman who stabbed 15 children and three teachers in a Beijing nursery on Wednesday may have been worried about losing his job, local media reported.
A four-year-old child died and several others are seriously injured
The nursery is to shut in September, prompting speculation that Xu Heping - who has a history of mental illness - feared being made redundant.
The attack has shocked China and prompted questions as to how Mr Xu had been given such a job.
Meanwhile, school officials have given details of how the attack took place.
The children were playing in the kindergarten schoolyard at the time of the incident, according to the China Daily newspaper.
The school cook told officials she heard screaming, and rushed outside to see the suspect frantically slashing at the children with a kitchen knife.
Mr Xu had apparently locked an iron door behind him before lashing out, denying the children an escape route.
Teachers made a brave attempt to wrest the knife from the suspect, according to the China Daily, but it was not until the police were called that the man was overpowered.
"It was a miserable scene," said Wang Bin, director of the hospital's security department.
"There was fresh blood everywhere - on the faces of the children, on the white working clothes of the teachers and on the floor," he told the China Daily.
Thirteen of the 15 young victims are children of staff who worked in the adjacent hospital.
"Because of the profession, doctors can't stay at home and take care of the children during the summer vacation," said one physician.
Before Wednesday's attack, Mr Xu had shown little indication of what was to come, according to media reports.
He delivered a newspaper to the school head's office, as he did every morning, and even asked her if there was anything else he could do.
Only a milk delivery man said Mr Xu looked unusually unhappy on Wednesday morning, according to China News Service.
Police and city officials said Mr Xu had a history of schizophrenia.
"Due to illness, Xu Heping was hospitalised at the Beijing Anding Hospital for treatment from 11 May to 24 September 1999,"
the Beijing government information office said in a statement.