(CNN) — Two New Jersey veterans say now-Congressman George Santos promised to raise funds for lifesaving surgery for one of their dogs in 2016, then became elusive and took off with the money.

Santos, the embattled freshman Republican, faces growing pressure to resign after he lied and misrepresented his educational, work, and family history. Santos has admitted to "embellishing" his resume, but has maintained he is "not a criminal."

Rich Osthoff, a US Navy veteran, told CNN his pit bull Sapphire began developing a tumor in 2015, and it continued to grow in 2016. Osthoff said he was homeless, living in a tent, at the time after losing his job and house.

Osthoff's mentor and friend Michael Boll, founder of New Jersey Veterans Network, told CNN he took Osthoff under his wing as part of the charity's mentorship program and tried to get help for his dog.

Boll said a mutual friend connected the two veterans with Santos, who told them Santos was frequently involved with helping and rescuing animals. Boll and Osthoff both knew Santos by the name Anthony Devolder, they said.

Santos set up a GoFundMe for Osthoff's pit bull, Sapphire, Boll said. A post from the Facebook profile of George Devolder links to a GoFundMe raising surgery funds for the dog.

"Sapphire is a 10 year old red nose pit bull that has been keeping this man company, she dose [sic] not deserve to die because of this tumor, she deserves to be treated and cared for," the Facebook post reads in part. "Will you help this baby and her daddy stay together for a few more years? Does he not deserve to have her? Let's all come together to help this family of two stay healthy!" the post says.

CNN has reached out to Santos' lawyer and his congressional office for comment. Santos told the news outlet Semafor that the story, first reported by Patch.com, was "fake" and that he had "no clue who this is."

The fundraiser eventually raised around $3,000, according to Boll.

But things went south after Osthoff tried to access the GoFundMe money, he said.

Santos became uncooperative, according to Osthoff and Boll — at first saying Osthoff needed to take his dog to a veterinary clinic of Santos' choice, then claiming another clinic wouldn't accept Santos' form of payment.

"I had to jump through hoops and do everything his way," Osthoff told CNN. "He was just totally ,totally difficult. One obstacle after another."

At one point, Santos told Osthoff directly that he wouldn't be getting the money. Osthoff said he accused Santos of running a bogus charity, and Santos became confrontational.

"He got so angry with me and he blew up and refused to give me the money and then just wouldn't answer the calls anymore," he said.

In a statement to CNN, GoFundMe said it removed the fundraiser from its platform after receiving a report about it.

"When we received a report of an issue with this fundraiser in late 2016, our trust and safety team sought proof of the delivery of funds from the organizer. The organizer failed to respond, which led to the fundraiser being removed and the email associated with that account prohibited from further use on our platform. GoFundMe has a zero tolerance policy for misuse of our platform and cooperates with law enforcement investigations of those accused of wrongdoing."

Boll tried to act as a mediator between the two, he said, with no luck.

"Anthony pretty much was unhappy with anything I was saying and was reluctant to even speak with me anymore," Boll said.

Santos eventually stopped replying to messages from Boll and Osthoff, and Osthoff says he never received payment from the fundraiser.

Osthoff said his dog passed away about six months after his last contact with Santos.

His dog, Sapphire, "was my little savior," he told CNN. "She kept me on this planet."

Osthoff said he had to panhandle for the money to pay for her euthanization.

Osthoff said he contacted the police about his interactions with Santos but said "it didn't go anywhere at all."

Because Santos went by a different name when the two veterans were in contact with him, Osthoff said he didn't know Anthony Devolder and George Santos were the same person until recently.

"In December I started seeing him on TV," Osthoff told CNN. "I recognized his face, and it just turned my stomach when I saw him."

"That he was now given a position where he affects thousands of people's lives ... It's really disheartening to know that," Boll said.

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