Police arrived at 6:41 a.m. to East Chicago Light House Charter School, located at 3916 Pulaski Street, in East Chicago, Indiana for a death investigation, police said.
Officers were led to a second-floor stairwell landing by school maintenance staff, where they found a deceased man.
The man has been identified as 47-year-old Craig Jones of Gary. He was a teacher at the school, East Chicago police said.
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Investigators said Jones had told relatives he was working late at school on Thursday night, and he later requested a ride home from a family member. When someone arrived at the school to pick up up around 10:30 p.m., Jones did not exit the building or answer phone calls.
The teacher's cause of death was not immediately known.
The Lake County Prosecutor's Homicide Task Force continues to investigate, but no foul play is suspected.
No further information was immediately available.