Two prison guards were fatally shot while on duty in what authorities believe was a murder-suicide that might have stemmed from a domestic dispute.

The names of the guards were not released late Sunday night after the shootings, but they were identified as a man and a woman in their 30s who had joined the staff of the Chillicothe Correctional Center, a women's prison, this summer.

"We've never had anything of this type" happen before, said prison superintendent Jennifer Miller.

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Officials declined to say which of the two fired the shots or what led to the shootings, citing the ongoing investigation.

Several people witnessed the shootings outside a building that houses a library and classroom. Prison officials said only the two guards were involved in the shooting.

Prison guards at the 525-bed prison are not allowed to carry guns for their jobs, but while there are occasionally random searches, they do not have to pass through metal detectors, Miller said.