The family of a controversial anti-vaccine doctor who was recently found dead in an apparent suicide have appealed to the public to help them raise money in order to launch 'an exhaustive investigation into the possibility of foul play'.

The body of Dr. James Jeffrey Bradstreet - who ran a private practice in Georgia 'treating children with Autism' using unconventional and polarizing methods - was found by a fisherman in the Rocky Broad River in Chimney Rock, North Carolina, on June 19.

He died on a gunshot to the chest. There was a handgun found nearby, and police say the death appeared to be self-inflicted.

But Bradstreet's family and supporters are crying foul and believe there is much more to the story, especially after it was revealed that agents from the US Food and Drug Administration searched his office for unknown reasons just days before he turned up dead.

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Mysterious death: Anti-vaccine Dr Jeff Bradstreet was found dead in a North Carolina river on June 19 following an apparent suicide. His family and many supporters now say there is more to the story

Scene: The body of Dr. James Jeffrey Bradstreet was found by fisherman in the Rocky Broad River in Chimney Rock, North Carolina, on June 19

'Jeff dedicated his life's work to finding answers, always pushing the envelope, and never giving up, even at the risk of being perceived as controversial,' wrote his niece, Cali Bradstreet Howell, on the GoFundMe website.

'Now, in this moment, we find ourselves in a position, where we too are in search for answers… and we intend on finding them.'

The GoFundMe page had raised over $20,000 as of Monday.

Bradstreet's Wellness Center in Buford used a 'mercury toxicity treatment' - among others - as an attempt to cure autism.

He believed the heavy metal was a leading factor in the development of childhood autism and that it was supposedly introduced into the body by vaccines.

He also published autism research based on the disputed claim vaccines cause autism.

The medical community says such claims have been disproved.

Dr. Peter Jay Hotez, Dean for the National School of Tropical Medicine at Baylor College of Medicine, told The Washington Post that this kind of mercury therapy is 'dangerous and without any benefit'.

The FDA has warned against such 'chelation therapies', saying they can cause 'life-threatening outcomes'.

Bradstreet's clinic was recently raided by agents from the FDA who were receiving assistance from the Georgia Drugs and Narcotics Agency, the Gwinnet Daily Post reported.

Bradstreet published autism research based on the disputed claim that vaccines cause autism (stock photo)

'The FDA has yet to reveal why agents searched the office of the doctor, reportedly a former pastor who has been controversial for well over a decade,' the newspaper reported.

Bradstreet is from Braselton, Georgia.

He went from being a pastor to attending the University of South Florida, where he received a medical degree, and completed his residency at the Wilford Hall USAF Medical Center in Texas.

His dedication to autism came after his son was diagnosed with the condition.

'Autism taught me more about medicine than medical school did,' he once said at a conference, The Epoch Times reported.

While his family haven't explicitly said they believe he was murdered, his supporters have.

'Self-inflicted? In the chest? I'm not buying this,' one person commented to Fox News, inforwars.com reported.

'This was a doctor who had access to pharmaceuticals of all kinds. This was a religious man with a thriving medical practice. Sorry, but this stinks of murder and cover-up.'

Bradstreet's clinic was raided by FDA agents with assistance from the Georgia Drugs and Narcotics Agency

His body was sent to Wake Forest Baptist Medical Center for an autopsy on June 23 and the case is still under investigation by the Rutherford County Sheriff's Office.

The investigator from the sheriff's office, Jamie Keever, said: 'I've talked to some of those people today.

'I don't know what to say. They have a right to their opinion.'

Fiona O'Leary of Autistic Rights Together [ART], responded to Bradstreet's death and the call for an investigation into his death.

She said: 'While it is very sad to hear of the death of Dr Bradstreet in such tragic circumstances, it is important to consider his position as one of the world's leading practitioners in the field of bio-medical treatments for autism.

O'Leary continued: 'Many of these so called 'treatments' are unlicensed and unproven to be of any benefit to autistic people, indeed many can have serious and dangerous side effects on an individual's health and well being.

'Many supporters of Dr Bradstreet and the bio-medical industry are hailing him as a hero, claiming foul play at the hands of the government, yet the truth is more simple perhaps.