Photo: The Canadian Press

An eight-year-old student took a kitchen knife to a central Minnesota elementary school and randomly attacked three other children Monday, authorities said.

Police Chief Perry Beise said the victims — aged 8, 9 and 13 — suffered "superficial wounds" requiring stitches in the attack at Pleasantview Elementary in Sauk Rapids. No one else was hurt.

Beise told The Associated Press he didn't know why the boy did it.

"If I could answer that question I would," the police chief said. "He randomly cut three students then walked into the office and set the knife down."

School Superintendent Bruce Watkins said the boy lashed out at the other students until an adult intervened. The incident lasted about 5 minutes and took place in a school hallway.

The incident happened about 7:15 a.m. as students were arriving for class, Watkins told the Star Tribune of Minneapolis. After putting his backpack away, the second-grade student took out a knife and slashed three students with it, the superintendent said. School officials immediately called police and an ambulance.

By the time officers arrived, Beise said, the boy was in an office with a counsellor and the three injured students were being treated by the school nurse. He said the boy was co-operative with investigators. He said he didn't know if the boy had been bullied, or if he had mental health issues.

Beise said the boy was released to his parents. The police report will be forwarded to the Benton County Attorney's Office.

"They don't charge children this young with crimes," the chief said "You try to get them treatment and help them be successful. It's also possible that human services will become involved in some way."

In an email to parents, school officials said that the parents of the three injured students chose to take their children home or to get additional medical attention on their own.

One of the injured children is a seventh-grader who was waiting to catch a transfer bus. The other two are Pleasantview Elementary students.

Watkins said the school made mental health counsellors available to students and staff. Classes went on as scheduled. The attacker will not be allowed back in school, the superintendent said.