The Upton County Sheriff's Office says Billy "Bubba" Kennedy died late Wednesday at the store in McCamey, some 50 miles south of Odessa.
The 38-year-old Kennedy encountered a man and several shots were fired. The unidentified suspect is in custody and being treated for multiple gunshot wounds.
Texas Rangers are investigating the shooting.
No other information was immediately available.
Kennedy is the second Upton County deputy to be killed in approximately a year. Deputy Mike Smith died in June 2012 when his patrol car was struck by a tractor-trailer while en route to an emergency call.
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