Baker, 29, who joined the Illinois Army National Guard at age 18, was in the middle of running two miles Friday at a Michigan training center when colleagues said he stopped.
They called 911 and the father of four girls died en route to Sparrow Hospital in Lansing, Mich., the Chicago Tribune reported.
His official cause of death wasn't reported.
"Jerome served with the Illinois National Guard for 11 years building a reputation as an intelligent non-commissioned officer and mentor," Brig. Gen. Daniel M. Krumrei, the guard's adjutant general, said in a statement.
Baker was promoted nearly a year ago to non-commissioned officer in charge of readiness for Company G, 634th Brigade Support Battalion, 33rd Infantry Brigade Combat Team, the newspaper said.
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