Citizens for Responsibility and Ethics in Washington, or CREW, originally received Secret Service documents in March that showed that Secret Service protection for the trip cost at least $17,000, a fraction of the more than $75,000 it actually cost taxpayers. However, those numbers looked fishy to CREW, since it did not make any mention of flight costs, nor it did it account for Trump Jr.'s trip to Mongolia's capital city, Ulaanbaatar, where he had a secretive meeting with Mongolian President Khaltmaagiin Battulga, according to CREW.

"If just one of Don Jr's trophy hunting trips cost more than $75,000, it's staggering to think how high the Trump family's total bill with taxpayers must be," CREW tweeted while sharing a picture of an argali sheep.

If just one of Don Jr’s trophy hunting trips cost more than $75,000, it’s staggering to think how high the Trump family's total bill with taxpayers must be.https://t.co/NIpQpgZjAb

— Citizens for Ethics (@CREWcrew) June 9, 2020

As ProPublica originally reported, the trip was pockmarked with corruption. Trump Jr. did not actually have the proper permits to hunt rare argali sheep, the largest species of sheep, noted for their giant horns.

The government of Mongolia issued him a permit retroactively, after Trump Jr. had already killed one and left the region. He also killed a red deer, which also needed a special permit. Also, Trump Jr. was accompanied by a major Republican donor, oil and gas company CEO Kevin Small.

The trip was arranged through a tourism company owned by a politically connected member of the Mongolian president's party, according to CREW, as HuffPost reported. The company helped arrange the special permit after the hunt had already taken place.

As CNN noted, argali are considered a near-threatened species, according to the Red List of Threatened Species, in large part due to trophy hunting.

Trump Jr. is a proud trophy hunter, often using his social media accounts to share images from his hunting and fishing trips to locations across the globe, including hunting elephants. His pride in big game hunts has netted him harsh criticism from animal rights' groups and conservationists.

After Trump Jr. killed an argali sheep last year at night with a laser scope, he instructed his guides not to dismember the animal. Instead, he instructed them to use an aluminum sheet to carry the carcass so as not to damage the fur and horns, as ProPublica reported.

That order to protect the fur and horns raised suspicion from the Center for Biological Diversity, which asked the U.S. Fish and Wildlife Service to investigate whether Trump Jr. imported argali parts back into the country — an illegal import, according to Forbes.

The Trump family averages about 1,000 more Secret Service trips per year than the Obama family did, according to the Treasury Department, as HuffPost reported. That's a 12-fold increase over the Obamas' travel. The president, as well as his daughter Ivanka and her husband Jared Kushner, all have kept their investment in their private companies, but travel on taxpayer money.

"Because of the overlap between the Trump Organization, the Trump White House and the Trump campaign, taxpayer money all too often ends up facilitating President Trump's conflicts of interest," CREW said in a statement earlier this year.