A spokeswoman during the briefing gave a revised figure of five dead and five injured, but the police department later clarified that those figures were not correct.
Police were alerted to the shooting shortly before 11am local time.
Responding officers “located a juvenile who they believe was responsible for this, deceased in the building”, Barnes said.
The White House said that President Joe Biden had been briefed on the shooting, while Wisconsin Governor Tony Evers said he was “closely monitoring the incident”.
“We are praying for the kids, educators, and entire Abundant Life school community as we await more information and are grateful for the first responders who are working quickly to respond,” the governor said on X.
-Agence France-Presse