The scene of the shooting in Normanhurst, Sydney, and John Edwards, inset.

By the time a police chopper was thundering over a home on Sydney's upper north shore on Friday morning in search of a double murderer, it was too late. John Edwards was already dead.

So, too, were his children; 15-year-old Jack and 13-year-old Jennifer.

Less than 12 hours earlier Edwards had fatally shot the two young teenagers in West Pennant Hills, before turning the murder weapon on himself at his home in Normanhurst, where an extensive police manhunt for the 68-year-old ended around 4.30am.

LINKEDIN Olga Edwards was estranged from her husband John Edwards

Those who knew Edwards have described him as a strange man; one who was anti-social, harsh to his children and even violent towards his son.

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It was around 5pm on Thursday afternoon when tragedy struck leafy West Pennant Hills.

Edwards had driven his white Commodore to the suburban home where his two children had been living with their 36-year-old mother Olga, Edwards' estranged wife.

There, he entered the property on Hull Road, shooting both of the young teenagers in their bedrooms, with handguns police have only described as "powerful."

On Friday police revealed the "premeditated and planned" shooting had come amid a two-year custody battle between Edwards and his wife, who had previously fled the Normanhurst family home with the children in the wake of a marriage breakdown.

From the outside the three-bedroom weatherboard house on Hull Road looks homely, with inviting front-facing white french doors.

But inside, police and ambulance service workers encountered scenes of horror when they entered around 5.20pm on Thursday.

Only moments later the children's mother Olga Edwards, a north shore solicitor, arrived home from work to her worst nightmare.

"We found two teenagers deceased in their bedroom," said NSW Ambulance Inspector Kevin McSweeney, a first responder.

A 68-year-old who police believe fatally shot his two teenage children in West Pennant Hills was found dead in Normanhurst.

"Unfortunately, at that time, there was nothing we could do to help them."

The house in Sydney's north-west was meant to be a safe haven for the trio, after they fled the Normanhurst home on Harris Road.

Instead it would be the site where the two young children and Olga had fought so hard to protect would be killed.

Who is John Edwards?

Investigators are now doggedly working to paint a picture of the man behind the gun.

Online Edwards boasted of a 37-year long career as a certified financial planner in Sydney.

According to a LinkedIn profile he held a graduate diploma of financial planning from Deakin University and was self-employed at John Edwards Financial Services.

He is also listed as being an authorised financial planner with AMP since 1995, however it is understood he left AMP in 2016.

To the outside world Edwards advertised his involvement with a local junior AFL club, the local chapter of the Lions and his volunteer work with the Rural Fire Service.

But neighbours have characterised the former financial services consultant as a recluse and unfriendly, especially since Edwards had left him in 2016 and taken the couple's two children with her.

"I was in the backyard one day and he said to me over the fence: 'Mate, she's left me and she's taken my kids. After sixteen years'," a neighbour, who did not want to be named, said on Friday in the aftermath of the murder-suicide.

Another neighbour who lived close to the Edwards' battleaxe block said Edwards was an "unhappy man" and detailed an incident in a Paris restaurant when he picked up his son by the neck and held him against the wall.

"Poor Jack probably copped the brunt of it ... he never had a kind word for those kids, he was very harsh."

Thursday's shooting came two days before Jack and Jennifer would break for school holidays.

Staff at Jack's school on Friday addressed the "sombre day" at a whole school assembly, with some in tears, as they confirmed the male victim was one of their own.

The Department of Education said students and staff at both Jack and Jennifer's schools had received counselling on Friday, which would be available during the school holidays.

'Very very distressed' after marriage breakdown

On Friday neighbours spoke of the protracted custody battle between Edwards and his estranged wife.

"It was a real mess," said one neighbour who had known the family for 15 years.

She said Edwards was "very very distressed" about the family breakdown, adding he had spoken to several neighbours about suicide before.

"It wouldn't have surprised me one bit [if he had killed himself]".

She was surprised, however, to hear police helicopters hovering above the home next door in the early hours of Friday morning.

"They were going 'Mr Edwards, come out. You are surrounded.' You know that's serious, you don't get that for a parking ticket."

The Herald understands Edwards had first obtained a gun licence last year, with authorities confirming he was the lawful registered owner of "multiple firearms," including the two handguns used in Thursday's shooting, which were registered earlier this year.

Both handguns were located at the Normanhurst property when police found Edwards' body on Friday morning, while all other firearms registered to the 68-year-old were also secured elsewhere.

A spokesman for the Ku-ring-gai Pistol Club confirmed on Friday that Edwards attempted to join their club in 2016, but was rejected.

While Acting Assistant Commissioner Brett McFadden confirmed there were no current AVOs against Edwards in place, Edwards had previously been subject to an AVO more than a decade ago, the terms of which are unknown.

In order to obtain a gun licence a person must not have been subject to an Apprehended Violence Order within the past 10 years.

From a family home to a 'creepy' property

After his wife and children left, the home that Edwards and the family had shared for 16 years fell into disrepair.

The pool, which a neighbour said she had never seen anyone use, was filled with a thick layer of algae and a trampoline sat off kilter in long grass.

"It wasn't even safe in there towards the end," said a neighbour.

The children had played on a rope that Jack had set up years ago, she said.

"Now it's just hanging there, it looks like a noose. It's so creepy."

WHERE TO GET HELP:

1737, Need to talk? Free call or text 1737 any time for support from a trained counsellor

Lifeline – 0800 543 354 or (09) 5222 999 within Auckland

Youthline – 0800 376 633, free text 234 or email talk@youthline.co.nz or online chat

Samaritans – 0800 726 666

Suicide Crisis Helpline – 0508 828 865 (0508 TAUTOKO)

What's Up – 0800 942 8787 (for 5–18 year olds). Phone counselling is available Monday to Friday, midday–11pm and weekends, 3pm–11pm. Online chat is available 7pm–10pm daily.

Kidsline – 0800 54 37 54 (0800 kidsline) for young people up to 18 years of age. Open 24/7.

thelowdown.co.nz – or email team@thelowdown.co.nz or free text 5626

Anxiety New Zealand - 0800 ANXIETY (0800 269 4389)

If it is an emergency or you, or someone you know, is at risk call 111.