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BATON ROUGE, La. — A married assistant principal in Louisiana faces murder charges after allegedly killing his pregnant co-worker because she threatened to make their relationship public, police said.

Robert Marks was already in jail for allegedly kidnapping the woman’s 3-year-old daughter when Baton Rouge police charged him with first degree murder and first-degree feticide in the death of40-year-old Lyntell Washington, who was once named “Teacher of the Year,” and her unborn child, according to WAFB.

One of Marks’ co-workers told police that Washington was carrying his child and had threatened to expose their relationship to his wife.

Farm workers found Washington’s badly-decomposed body in a ditch Tuesday north of I-10 in Iberville Parish, about 45 minutes outside of Baton Rouge.

An autopsy determined Washington died from a gunshot wound to the head.

Police arrested Marks on June 9 after Washington’s 3-year-old daughter was found alone in a parking lot near her mother’s abandoned car, which had blood spattered on the interior, according to the The Advocate.

When detectives arrived, the little girl told them, “Mom’s in the lake,” according to the police report.

Before his arrest, Marks worked at the Brookstown Magnet Honors Academy.

Washington, who worked at the same school as an instructional specialist, was given the “Teacher of the Year” award at the Eden Park Superintendent’s Academy.