Volunteers, divers, helicopters, all-terrain vehicles and members of the Australian Defence Force fanned out over some 470sq km to try to find the boy.
“Everything we have found to date … indicates that, as best as we know, Gus has wandered off from this property and we have not been able to locate him,” Parrott said.
“This is clearly now what appears to be a very tragic set of circumstances. We hold out hope we may be able to find Gus and return him to his family, but clearly that potential is diminishing as days go by.”
The ADF will be stood down on Friday afternoon and police officers will not remain on the property moving forward.
The assistant commissioner said investigations into the tragedy would continue.
“We will not rest until we can try to find the answer, why Gus has gone missing,” he said.
On Thursday, police warned the search operation had moved into a “recovery phase”.
Meanwhile, police phone lines have been flooded with “opinions” on the whereabouts of August, also known as Gus.
The boy’s family have released a photo of their curly-haired son, in the hopes of attracting new information.
But the photo has prompted unwanted calls from the public, Senior Constable Peter Williams told ABC Radio in Adelaide on Friday.
“I do remind people that the purpose of the image going out is for anyone who’s got actual information that may assist the investigation,” he said.
“We just ask people, we’re not after your opinions. We’re after help with the investigation.
“If it is just an opinion, perhaps keep it to yourself, but if you’ve got factual information, feel free to give us a call and provide that.”
Speaking to reporters on Thursday, Yorke Mid North Superintendent Mark Syrus said police had grave fears for the boy, who has been missing for almost a week without access to food or water, and had changed their rescue into a “recovery phase”.
“A 4-year-old doesn’t disappear into thin air. He has to be somewhere,” he said.
“Hopefully, he’s hanging in there alive, but we are now in recovery phase, and the fact he’s been gone over 100 hours and six days, that’s a long time to be out in the elements.”
Police released an image of the missing boy sitting at a table, featuring his light blond curly hair and hazel eyes, wearing a shirt with a Peppa Pig logo, stars and My Mummy written across the front.
Former neighbour Royce Player told reporters on Thursday that he thought rescuers “might’ve found him by now”.
“Doesn’t take much, and if he’s frightened he’ll be hiding. Let’s hope he’s still out there,” he said.
Player said the child was small, and could be easily missed if the rescue team was stretched metres apart.
“He’s not very big, so it doesn’t hurt to backtrack and go over your tracks several times,” he said.
Player used to live next door to the family and dropped everything to help the search efforts.
“I thought ‘Bugger this’ last night – I gotta do something,” he said, adding the little boy just “wants his mum”.
“I’m a parent, so yeah … well, I don’t know what it would be like, but I wouldn’t like to go through it myself.”
His disappearance has sparked a major search effort involving dozens of police, volunteers and rescue teams, who have been scouring the regional property and its surrounds for almost a week.
Five days into the search, police announced about 50 Australian Defence Force (ADF) personnel and a skilled tracker had been called in for assistance.
An ADF spokesman said they had “accepted a formal request” from the police to assist in the search and sent 48 personnel.
“Defence has accepted a formal request from South Australia Police to assist in the search for a missing 4-year-old boy near Yunta in the east of South Australia,” the spokesman told NewsWire.
Police delivered a breakthrough on Wednesday after a child’s footprint was discovered about 500m from his homestead.
“We’ve positively identified that it’s a child’s footprint,” Superintendent Syrus told ABC radio on Wednesday.
“It’s a very similar boot pattern to what Gus was wearing when he went missing.”
Despite the breakthrough, he told reporters on Thursday the footprint may have not been recent.
“That could have been there for a week,” he said.
“We’ve got to be careful we don’t funnel all our attention on that one little clue.”
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