A childhood friend of Gus Lamont's grandmother believes she is being targeted because of her gender transition and has claimed the little boy could have been snatched and killed by a bird of prey.

Bill Harbison, a semi-retired equine vet and loyal supporter of Josie Murray, voiced his extraordinary theories during her tell-all TV interview with Seven's Spotlight on Sunday night.

He accused police of discrimination against Ms Murray while offering his own explanation for Gus's disappearance.

'Wedge-tailed eagle can pick up a 20, 25 kilogram kangaroo and take it without much difficulty,' he said.

'Gus was 13 or 14 kilograms, so I'm not sure a mature wedge-tailed eagle would find that quite uncomfortable.'

The wedge-tailed eagle is Australia's largest raptor and one of the largest birds in the world. According to the Australian Museum, the species does include live prey in its diet.

The birds may also hunt in pairs or larger groups to attack and kill an animal as large as an adult kangaroo.

Australian wedge-tailed eagle specialist Dr Simon Cherriman has, however, since told Daily Mail that it is 'extremely unlikely an eagle could have been involved in the disappearance'.

'The maximum weight an adult wedge-tailed eagle can potentially carry is up to 5kg.

'One instance of one picking up, briefly carrying for a short distance and then dropping a small kangaroo was documented in 1980.

'This suggests the bird struggled to carry something weighing 5kg, so would not be able to lift a weight greater than 5kg.

'Most four-year-old boys weigh over 16kg, which is a weight that an eagle would not physically be capable of carrying.'

Dr Cherriman did concede that while a bird would not be able to lift Gus, his size was still comparable to some of the species' usual prey.

'Large raptors, including wedge-tailed eagles, regularly kill prey larger than themselves and weighing more than they are capable of carrying, including mature kangaroos.

'But it means the prey is killed and then usually eaten in situ over several days.

'If a child were killed by one or more eagles, its body would remain in place and the remains of inedible materials, like clothes, would be left or scattered to be found later.

'One would anticipate this is something that would have been detected during the multiple searches undertaken following Gus's disappearance.'

He also pointed out that while Gus was the right size to be hunted by the animal, it would be highly unusual for him to be targeted.

'The species is generally very shy, wary and scared of humans,' he said.

'There are a few reports of wedge-tailed eagles dive-bombing humans, such as hikers on peaks in mountainous terrain, and one record about a century ago of several eagles 'harassing' a few school-aged children walking home here in the Perth Hills.

'But these are very unusual cases and exceptions to the rule.'

Police have previously revealed no items of clothing or other evidence were found during the extensive searches of the land surrounding the property.

Mr Harbison also made the bombshell claim that he felt Ms Murray had been subjected to 'discrimination'.

He said he challenged police about 'targeting her because of her transgender situation - and they were mortally offended that I should say it'.

Today South Australia Deputy Police Commissioner Linda Williams slammed claims she had been unfairly targeted due to being transgender.

'The claim is nonsense. When we conduct an investigation, we always do it impartially. I am very proud of the professionalism shown by our officers.'

 Ms Murray's transition was also mentioned last week in court during her appearance on unrelated gun charges.

While Ms Murray pleaded guilty to owning an unregistered silencer, her ex-wife, Shannon Murray, provided a character reference in which she explained the pair were no longer in a relationship.

Shannon said they had separated after her husband transitioned from male to female and were now friends and business partners.

Shannon was not at the court hearing in person and did not appear in the interview.

While Sunday marked the first time Ms Murray had spoken publicly, Mr Harbison, who went to school with Gus's grandparents and was part of the initial search party, previously read a statement on behalf of the family about the boy's disappearance.

'I have been asked to read this statement on behalf of the family,' he said two days after Gus was last seen by Shannon playing outside their remote farmstead.

'We're devastated by the disappearance of our beloved Gus on Saturday afternoon. It comes as a shock to our family and friends, and we're struggling to comprehend what has happened.

'Gus's absence is felt by all of us and we miss him more than words can express. Our hearts are aching and we are holding on to hope that he will be found and returned safely.'

The statement went on to thank South Australia Police, revealing the family were 'incredibly grateful' for their efforts. 

It is a sentiment that no longer appears to be shared, with Josie criticising the investigation for allegedly missing key information, including unusual tyre tracks and a fresh footprint, before naming her as the main suspect in her grandson's death.

'We haven't got a body, we have no idea, but we feel he has been taken,' she said.

She then claimed police had ruled out an abducted because CCTV cameras showed nobody had entered the property, only for her to later discover one of the cameras was not working.

Ms Murray said when she raised her concern she was told 'no one showed up on the cameras' but had been 'lied to' because the 'camera wasn't working'.