The attack took place in the city of Uvalde in Texas in the USA, according to the health service, reports ABC News.
A suspected perpetrator has been arrested by the police, who do not provide any further information about the detainee.
In addition to the children, a 45-year-old was injured in the shooting that occurred on Tuesday.
The city's mayor Don McLaughlin tells ABC News that parents should be contacted before the authorities go out with more information