A 16-year-old male suspect was taken into custody without incident after shooting a 15-year-old girl in the cafeteria, officials said.
It was unclear whether the shooter and the victim knew each other. Authorities have said the girl was airlifted to a Dallas hospital.
Video from Texas Sky Ranger showed police surrounding Italy High School, where students were being evacuated to a neighboring building.
"This is a trying time for our community and our school", Joffre said, who added that the district was making arrangements for grief counselors to be available to students who needed them.
Joffre says the district is working to reunite parents with their children.
Italy, which promotes itself as "The Biggest Little Town In Texas", has about 2,000 residents and is located just off Interstate 35 between Dallas and Waco.
He said he had no information on her condition.
One student was injured after being shot at Italy High School Monday morning.
The Ellis County sheriff's office confirmed in the morning that students at Italy High School were being moved, "under guard", to a different location.
A message left with the school district was not immediately returned.
Sheriff's officials say there's been a shooting at a high school in a small town south of Dallas and a suspect is in custody.