Mother shares first photos of son Jack, 15, and daughter Jennifer, 13, killed by their father.

With AAP. 

Warning: This story deals with family violence and suicide.

On Thursday evening, at around 6.30pm, 36-year-old Olga Edwards returned to her West Pennant Hills home after work to find a ‘horrific scene’. It’s reported the mum-of-two collapsed from severe shock as she learned what had happened to her 15-year-old son, Jack, and 13-year-old daughter, Jennifer, at the hands of their father.

According to The Daily Telegraph, John Edwards, 68, hired a car so that when he pulled up outside the family home, his children wouldn’t know it was him. He timed the attack just before school holidays, so he knew his son and daughter would be at home alone without their mother. At around 5.20pm on Thursday, he shot his two teenaged children dead in a “planned and premeditated” attack in their Hull Road, West Pennant Hills home.

John Edwards was found dead in his Normanhurst home about 12 hours after his children’s bodies were found. Police believe he took his own life.

On Saturday afternoon, Olga Edwards requested the first images of her children be released, according to NSW Police.

Police told The Daily Telegraph the Edwards' children "were trying to hide in a bedroom and were huddled together when he opened fire".

Olga Edwards, a solicitor at Brown and Partners Solicitors in Woolwich, reportedly returned to her Hull Road home for the first time on Saturday.

Friends and neighbours have been leaving flowers and cards at a makeshift memorial outside the West Pennant Hills home which is still taped off by police.

The student leadership council at Pennant Hills High School, where one of the teenagers attended, said it was a "devastating" event.

"Today our hearts broke when we found out that one of our students was taken from us too soon," Penno Student Leadership Council said on Facebook on Friday.

"As a school, we will find the strength to get through these unfathomable experiences and unite to support each and every person in the community."

Police were aware of Edwards over past matters but he had no recent issues with the law.

He had been involved in a custody battle with Ms Edwards, for two years following the breakdown of their marriage.

But the nature of their relationship and any violent incidents between them is still being investigated.

Two "quite powerful" handguns registered in the father's name sometime this year and used to kill the children, were found at the Normanhurst home, Mr McFadden added.

A number of other guns owned by Edwards were also found.

Edwards, 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.

If you, or someone you know, is being subjected to domestic violence, call 1800 RESPECT (1800 737 732), or Relationships Australia, (1300 364 277).

Anyone across Australia experiencing a personal crisis or thinking about suicide can call Lifeline (13 11 14).