In the course of their investigations, police located the suspect-the children's 68-year-old father-deceased in his Normanhurst home at around 6 a.m. on Friday morning.
The mother, who arrived at the house shortly after the Thursday afternoon shooting, was treated by paramedics for severe shock before being taken into the care of friends and police.
Police are expected to address the media with more details this morning. "The 36-year-old wife had fought for custody of the children over the last two years".
Mr Edwards, who was described as a "recluse" by a neighbour, was a financial planner and volunteered with the NSW Rural Fire Service, Lions Club and Pennant Hills Junior AFL Club, according to his LinkedIn page.More news: Dele, Maguire head England into first semi-final in 28 years
The teenagers had been at home by themselves, police say.
"At this stage, the person of interest we are looking for is still at large but we believe this to be a targeted incident and there are no risks to the community at this time", Acting Assistant Commissioner McFadden said.
The father's body was found in his home in the early hours of Friday but police believe he took his life shortly after murdering his children.
Acting Assistant Commissioner McKendall confirmed there were no current AVOs in place, but said there had been "some custody hearings over the past two years".More news: Daniel Cormier claims UFC heavyweight championship with KO of Stipe Miocic
"The emergency service personnel responded to what can only be described as an horrific scene inside those premises", he said.
NSW Ambulance Inspector Kevin McSweeney told reporters that when paramedics arrived they "were confronted with an extremely distressing and stressful situation".
"It's a bad, awful tragedy", the prime minister told reporters on Friday.
At the scene on Thursday evening, forensic investigators wearing white protective suits could be seen walking up and down the street with torches and cameras. He was alerted to the incident when his daughter saw it on the news and contacted him before he came outside. It's understood the two teens' bodies were removed just before 6am the following day.More news: World Cup Quarter-Final match report Russian Federation v Croatia 07 July 2018
"It's made me a bit shakey", he said. Our hearts go out to the mother and to all of the family, and we mourn the loss of those young people. "It's so horrific ... especially for such young people to be the ones killed".