The teenagers' 36-year-old mother Olga, a solicitor, had to be treated for severe shock when she arrived at the scene.
Earlier, in a statement, NSW Police said: ‘Two teenagers have died following a suspected domestic violence-related incident in Sydney’s north-west.
‘Emergency services were called to the home on Hull Road at West Pennant Hills, responding to reports of gunshots about 5.20pm (Thursday 5 July 2018).
‘When police arrived, they found a teenage boy and girl deceased at the scene. A woman, who lives at the home, is being treated for severe shock.’
Two guns were found alongside the dead man.
'Those handguns came into his [Edwards’] possession lawfully earlier this year,’ Acting Assistant Commissioner Brett McFadden said on Friday.
‘This was a planned activity on the part of the 68-year-old male ... shortly thereafter he has attended the address in Normanhurst and taken his own life.’
If you have been affected by the issues raised in this report, help is available from Lifeline on 13 11 14.