A Punjab Police head constable allegedly shot dead his son and seriously injured his wife and second son before shooting himself dead at their under-construction house in Jhujhar Nagar on Mansa Khurd Road on Tuesday morning.The family had shifted to the house on Monday evening, sources said.Head Constable Gurwinder Singh, who was deployed as the gunman of the Mansa Deputy Commissioner, allegedly opened fire on his family members before shooting himself dead.The injured were referred to a hospital in Bathinda for treatment.Mansa Senior Superintendent of Police Vaibhav Chaudhary, who visited the spot, said the police had initiated an investigation.“The preliminary investigation suggests that the incident stemmed from a family dispute. We have seized the official weapon of the deceased from the spot. A forensic team is collecting the evidence,” he said.An elderly woman living in the neighbourhood said the injured woman was lying outside her residence at around 6.30 am and had asked them to save her.