Police are investigating how Sydney father John Edwards obtained a firearms licence and was allowed to take weapons from a gun range before shooting dead his teenage son and daughter.

Jack, 15, and Jennifer, 13, died huddled together in their bedroom in West Pennant Hills Sydney just before 5.20pm on Thursday after their 68-year-old father shot them numerous times.

On Saturday the children’s mother, Olga Edwards, returned to the family home and released photographs to the media of her children, two days after discovering their bodies.

NSW Police Acting Assistant Commissioner Brett McFadden said Ms Edwards was in shock.

“I can’t even imagine the stress and the heartache that she is going through right now,” Mr McFadden told reporters.

Mr Edward’s body was found at his home in Normanhurst, a suburb on Sydney’s Upper North Shore, about five kilometres from where the children were killed.

Police said Mr Edwards had been involved in custody hearings over the two children during the past two years.

Gun Control Australia branded Mr Edwards’ gun licence and ownership a “system failure” and called for robust new family law firearm safety checks to better protect women and children from gun violence.

The anti-gun lobby has issued recommendations that include compulsory firearm safety checks once a custody proceeding has been lodged in the Family Court, plus a “spousal notification” for all new firearm licence and permit applications.

GCA director Samantha Lee told The New Daily that current gun laws were failing to adequately protect women and children from gun violence because the law requires an Apprehended Violence Order or criminal offence charge before a firearm licence can be revoked or suspended.

“What GCA wants to see happen is a more pro-active approach which gives woman a voice in the gun licence application or acquisition,” Ms Lee said.

A senior police officer told The Australian they were “mystified” as to how Mr Edwards had finally succeeded in obtaining a gun licence after 10 years of failed attempts.

“The big question here, which we absolutely can’t understand, is did the …court know that he had firearms when they handed down a judgement saying he shouldn’t be allowed anywhere near his family?” a police source told the newspaper.

It is understood Mr Edwards had been denied membership by several pistol clubs in the Sydney area.

The New Daily contacted a number of gun clubs in Sydney and New South Wales on Saturday afternoon, but members declined to comment.

A spokesman for the Ku-ring-gai Pistol Club told The Daily Telegraph Mr Edwards approached the club in December 2016, but was refused entrance.

“He came to our club some time ago and we were not very happy with him,” he said. “There were too many things about him we didn’t feel comfortable with.”