"Two of the victims were shot," CNN quoted Butler County Sheriff Richard Jones as saying.
"The other two were injured either by shrapnel from the handgun or by injuries getting away from the active shooter," he said.
The shooting happened at Madison Junior-Senior High School in Middletown, Ohio.
The sheriff identified the suspected gunman as James Austin Hancock. He was taken into custody and faces charges as a juvenile of attempted murder, felonious assault, inducing panic, and making terroristic threats.