Washington County Sheriff Jeffrey Murphy said Monahan fired at a car with four people inside as they were trying to turn around in the driveway. The group apparently realized they were at the wrong address.
Kaylin Gillis was struck by a bullet. The New York Times reports her friends drove about six miles to a town where they could call 911.
CBS News reported first responders found the car on Cemetery Road in Salem but were unable to save Gillis's life.
“She was an innocent young girl who was out with friends looking for another friend’s house,” Murphy said.
Officers arrested Monahan after he refused to leave his home for about an hour.
"There was clearly no threat from anybody in the vehicle," the sheriff said.
An attorney for Monahan said he runs a contracting business.
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“It was a series of errors which resulted in a tragedy,” Kurt Mausert said. He declined to give more details.
A GoFundMe account set up to help with Gillis's funeral expenses had more than $54,000 in donations Tuesday morning.
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