The shooting occurred at the office of District Judge Daniel Shimshock in the Fayette County Magistrate Court in Masontown. Four people were transported to a hospital, a spokesperson for the Fayette County Emergency Management told ABC News.
It's unclear if the person pronounced dead at the scene is the suspect or a victim.
A law enforcement official was among the shooting victims, the Pennsylvania State Police's Troop B, which handles Fayette County, wrote on Twitter.
At this time we have multiple victims and injuries one being a law enforcement official. There is heavy police presence. We are asking the public to stay away from the area at this time.— TroopB (@PSPTroopBPIO) September 19, 2018
More than a dozen police officers surrounded the building in the aftermath of the shooting, aerial footage shot by ABC Pittsburgh affiliate WTAE showed.
David Kaiser, an attorney who was at the judge's office when the shooting happened, said he heard an argument outside the judge's office preceding the shooting.
A witness told WTAE that a man opened fire on a woman running across the street.
DEVELOPING: We will add more details to this report as they become available.
ABC News and the Associated Press contributed to this report.