A gunman opened fire outside a crowded Pennsylvania courtroom Wednesday afternoon, shooting at police and others before an officer fired multiple shots at him, killing him.

Fayette County District Attorney Richard Bower said Wednesday evening that a German Township police officer shot and killed the gunman after he entered the lobby in Masontown with a handgun drawn and opened fire injuring four people. Bower declined to name the gunman, saying only that he was due in court on charges related to a recent domestic violence incident.

Bower said Masontown police Sgt. R. Scott Miller first encount...