The suspect’s body was found at another home in Normanhurst, about seven kilometres from the scene of the initial killings, early on Friday morning, NSW Police have confirmed.
It’s believed the man was the father of the children and aged in his 50s.
The 15-year-old boy and a 13-year-old girl were found shot dead in their bedrooms at a house in Hull Road at West Pennant Hills shortly before 5.30pm on Thursday.
— 7 News Sydney (@7NewsSydney) July 5, 2018
Their mother, 36, arrived shortly after police and was treated by paramedics for severe shock.
Det Supt McFadden said it was a “targeted attack”.
“We do believe that it may well be domestic violence-related and our focus at the moment is on the investigation to locate our person of interest,” he told reporters late on Thursday.
NSW Ambulance Inspector Kevin Sweeney said paramedics were faced with an “extremely distressing and stressful situation”.
Police inquiries continue and an extensive forensic examination led by the homicide squad is underway.
It’s unclear how many shots were fired but detectives are speaking with several witnesses to determine what happened.
Those seeking support are urged to call 1800 RESPECT (1800 737 732) or Lifeline on 13 11 14.