Three people died following a property dispute between cousins in the Dal area of Upper Kurram, police said.
According to police, Asghar Hussain and his brother Asad Ali were killed in the firing incident.
A third relative, Kamal Hussain, suffered a fatal heart attack after seeing the bodies of the two victims, police added.
The bodies were shifted to the District Headquarters Hospital in Parachinar.
Police said an investigation into the incident was underway.