It was the morning after the last member of their family, father Mark Tromp, 51, had been found and the youngest of the children – Ella and Mitch – said they were just happy their dad had been found alive and well.

"More than anything, we're just happy Dad's alive and he's going to come back home and all the family is going to come back home, and we can get back to normal," Ella said on Sunday.

Mitch, 25, and Ella, 22, spoke to the media in the front yard of their home in Silvan, in the Yarra Ranges east of Melbourne, as a thank-you to the public.

Read the full transcript here

It was a passerby who had spotted their father walking along a road in the outskirts of Wangaratta late on Saturday afternoon and phoned police.

"I just want to thank everyone – the media, Mark Knight at the local police station, family, friends – there's been so much support and so much help from everyone," Mitch said.

But questions remain about how and why their family became gripped with paranoia, convinced someone was after them and terrified they were being watched, tracked and followed.

The paranoia centred on their financial affairs, specifically that someone was trying to steal their money.

That anxiety built up to the point that the parents fled the house, taking their children with them, on Monday.

Both Mitch and Ella left their family and found their way home. Sister Riana had stowed away in the back of a stranger's car before she was discovered and taken to hospital. Their mother, Jacoba, was found wandering in Yass, while Mark was last seen in Wangaratta before he disappeared.

Mitchell previously said there had been no current or previous diagnoses of mental illness, but it is believed one of his parents experienced a mental health episode, which spread through their family until everyone, apart from Mitchell, believed they were in serious danger.

"I can see everyone's questions," he said. "I can see why they want to know, but it's a family matter. I just want the family to be able to come back together and everything to work itself out."

He and Ella said they would await the outcome of a police investigation for concrete answers.

"I still feel confused. I think our state of minds weren't in the best place," Ella said.

Their father was cleared at the police station on Saturday night by a medical assessor from Albury Wodonga Health and released into the care of his police officer brother Ken.

Mitch and Ella said they couldn't wait for him to come home so they could hug him.

"It's the first time I haven't woken up crying in two days," Mitch said.

"I think I'll cry when I see Dad," Ella added.

Both children have spoken to their father on the phone.

"He was my dad; he was just how he always is and it was so great to hear from him," Mitch said.

"I just wanted to hear his voice and we'll go through those details [about where he had been] later," Ella said.

"He's well and he said he just wanted to come back home and get back to work."

Jacoba – known as Coby – and Riana both remain in hospital in Goulburn being treated by mental health clinicians.

Mitch and Ella said their mother and sister were both doing well, but they were unsure of when they would be allowed to return home.

Mitch said he wished he had never left his family. "I had to go with the family because I wanted to see where they were going – I couldn't leave them," he said.

But it got to the point where he had had enough and didn't believe their fear was based on anything real. He left his family in Bathurst, NSW, and took a series of trains home.

"I thought getting out was the best idea for me at the time," he said. "In hindsight, I should have tried to stay with them and try and help to bring them back around and talk to them more, but I got out of the car."

The rest of the family continued driving to Jenolan Caves. Ella, who with her sister left their parents once they got there, said she was still confused by what had happened.

"I was confused about the whole situation, as I still am now," she said. "I just wanted to get home to feed my horses."

Ella and Riana had stolen a car at Jenolan Caves, and Ella drove it back to Silvan.

Mark and Jacoba drove south to Wangaratta, where they separated. Jacoba took public transport back up north to Yass, while Mark dumped the Peugeot, which belonged to Ella, in a Wangaratta side street on Wednesday night.

Yarra Ranges sergeant Mark Knight – who led the investigation and knows the family – said that despite the family's fear they were being followed, no one was after them and they were not being pursued. Police have not found evidence suggesting the family's money was being targeted by a thief.

Sergeant Knight said there had been no previous diagnosed mental health conditions among the family and there was no evidence of drug taking or drug psychosis.

There is no suggestion of carbon monoxide poisoning, which can cause psychosis.

The family have no debts and their businesses – an earth-moving company and berry farm – are successful.

Sergeant Knight said he experienced "sheer relief and happiness" when he was told Mr Tromp had been found.

"It brought us an overwhelming relief," he said.

He and three other officers, including a retired policeman who volunteered his help, worked out of the Monbulk police station investigating reported sightings of the man they knew well.

Their colleague Ken Tromp, Mark's brother, led the search in Wangaratta.

​Timeline:

Monday, August 29: The Tromps leave the family home in Ella's Peugeot, terrified someone is after them. During the course of the drive, it's discovered Mitchell has brought his phone with him. He throws it out of the window near Warburton, about 32 kilometres from the family home. The family continues driving towards Bathurst.

Tuesday, August 30: Mitchell decides he wants to go home. He leaves the family at Kelso, a suburb of Bathurst, about 7am and makes his way to Sydney. The rest of the family continue on to the Jenolan Caves. That afternoon, they decide to split up. Ella and Riana acquire a car, make their way to Goulburn then go their separate ways. Riana is found along the highway after stealing a lift in a ute and is taken to the local hospital due to stress-related issues. Ella drives back to the family home in Silvan. Parents Mark and Jacoba are reported missing and that afternoon police attend the family home to find credit cards and mobile phones lying around the house and car keys in ignitions.

Wednesday, August 31: Mitchell arrives at the family home in the morning after catching the overnight train from Sydney. That afternoon, police search the Jenolan Caves area for Mark and Jacoba but are unable to find them. The couple drive south to Wangaratta where they separate. Jacoba takes public transport to Yass and Mark is seen leaving the Peugeot, with keys in the ignition, in a side street.

Thursday, September 1: Police are notified in the early hours of the morning that the family car has been located in Wangaratta and that a lone man was seen walking away from the car. It is believed this man was Mark. Later in the day, Jacoba is taken to Yass District Hospital after a local found her wandering around town.

Saturday, September 3: Mark Tromp is found by police after a passer-by saw him walking along Greta Road, on the outskirts of Wangaratta, shortly before 6pm.

With Tom Cowie, Shana Morgan and Goya Dmytryshchak​

For help or information call Lifeline on 131 114.