Police identified the suspect as 26-year-old Carlos Borbon.
Police initially thought Borbon may have been armed with a gun, so North Babylon School District locked down its high school and a nearby elementary school.
Around 3:30, police attempted to place a camera in the building to further increased communication.
Borbon threw a fire extinguisher at a sergeant and came at him down the stairway, authorities said.
The sergeant, who was not identified, suffered an injury to his leg. Officers arrested Borbon, who suffered minor injuries to his head. He was taken to a local hospital.
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