ALTOONA, Pa. (AP) -- A central Pennsylvania police officer has pleaded guilty to disorderly conduct and was fined $1,000 for allegedly punching another man after a concert near Pittsburgh in September. Altoona police Chief Janice Freehling says Friday's plea by 27-year-old Officer Matthew Plummer will end an internal investigation, for which Plummer still faces unspecified discipline. Plummer was off-duty Sept. 7 in Hanover Township, Washington County, when police there allege he punched a man who bared his buttocks at a bus that took Plummer, other officers and 911 dispatchers to the Kid Rock concert at First Niagara Pavilion. That's about 25 miles west of Pittsburgh and 100 miles from Altoona. Plummer's attorney had previously argued the officer punched the man in self-defense. The other man was fined $35 for disorderly conduct, and spent several days in the hospital.