The Minnesota elementary school student used a similar knife to attack his classmates.
Staff and students at the school will be able to speak with mental health counselors if needed, according to KARE.
Watkins said the incident lasted approximately five minutes before the student was stopped by "adult intervention".
The incident took place before school started.
Ambulances as well as armed police were seen at the school, local media sn.dk reports. Watkins says he believes the injuries aren't life-threatening, and the students were taken to the hospital by their parents.
The suspect was taken into custody by Sauk Rapids Police and due to his age, was later released to his parents.More news: Malaga vs Real Madrid: Zidane to drop Ronaldo for LaLiga clash
Watkins says a message was sent to parents to let them know about the incident.
Authorities in central Minnesota say an 8-year-old boy brought a kitchen knife to school Monday and randomly cut three other students. Mental health professionals are available on site at Pleasantview Elementary. He says the boy cooperated with investigators.
A number of armed police were despatched to the school in the town of Ishøj near Copenhagen after the student, who was previously expelled from the school, reportedly made the threats.
"They don't charge children this young with crimes", the chief said "You try to get them treatment and help them be successful". The incident resulted in three students being injured and the aggressor was contained in the office.
It happened at about 7:15 a.m. Monday. The police said that according to the victim's mother, they both were earning livelihood by doing labour works and Prahalad Sao was also pursuing his academic future.