A couple celebrating a milestone wedding anniversary claims they have captured footage of the legendary Bigfoot, sparking an online frenzy.

Earlier this week, Shannon Parker from the US state of Wyoming shared footage to Facebook of what she believes is proof that the illusive Bigfoot is real.

The footage and photos were captured on October 8, when Parker and her husband Stetson Tyler were on a train from Silverton to Durango in Colorado.

Parker had asked Tyler to help her spot some elk in the mountains – and that’s when they saw what they believe is Bigfoot.

“It was at least six, seven feet or taller (1.8-2.1 metres). It matched the sage in the mountains so much that he’s like camouflaged when crouching down … if you asked before our trip, we would have said maybe [Bigfoot] could be real, but now we’re convinced,” she told the New York Post.

According to Parker, the train’s conductor told people there had been previous sightings in the lonely rural area of something that did not appear to be human.

“He said that he went out snowshoeing in those mountains before and had seen footprints that were larger and of much bigger stride than snowshoes would have been,” Parker said.

“He has seen unexplainable things as well.”

Parker’s post has since been shared nearly 3000 times – and has about two dozen comments. Some expressed their belief in the footage, while others were more sceptical. One even said the couple had probably seen someone in a Halloween costume.

“What were y’all drinking?” one user asked.

The legend of Bigfoot

Bigfoot, also commonly known as Sasquatch, is a large and hairy human-like mythical creature that has long been said to live in forests and mountains in North America,

The Washington State Military Department has noted that the legends date from earlier than recorded history – native Americans have long reported seeing a huge creature, covered in hair, in forests.

There are many names for the creature, though “Bigfoot” is most common in the US. Sightings generally occur in the mountainous western region of North America.

“North American settlers started reporting sightings during the late 1800s and into the 1900s, with the occasional finding of footprints, sporadic encounters and even a few grainy photos and videos adding to the mystery,” Washington State Military Department says.

“Those who claim to have seen Bigfoot have described everything from a large, upright ape to an actual hairy human, sometimes standing over eight feet tall and described as powerfully built. The debate and research continue.”

There days there are even organisations devoted to studying and documenting Bigfoot, and trying to prove it exists. They include dedicated groups who regularly searching forests across the US north-west, looking for that ultimate proof.

Parker’s reports sparked new theories about who – or what – was behind her sighting. On Reddit, users speculated someone from Colorado campervan company Sasquatch Expedition Campers could be involved.

But company co-founder Kass Kremer issued a denial, of sorts.

“We, The Sasquatch Crew, feel compelled to address recent allegations and rumours that have been circulating, suggesting our involvement in the train sighting. We want to make it unequivocally clear: It wasn’t us,” the company wrote on Facebook.

The statement was written on paper next to clumps of dark hair or fur. It was accompanied by a photo showing someone working on a campervan while wearing Sasquatch hands and feet.