And over a five-day period just last month, three others tourists mysteriously died in their rooms at another Dominican resort.
Robert Bell Wallace, 67, from California fell ill and died at the Hard Rock Hotel & Casino resort in Punta Cana, on April 14.
She said: "He started feeling very sick, he had blood in his urine and stool right afterward".
Arnold further explained that the hotel doctor had checked Wallace, and decided on April 13 that he had to be hospitalized.
"He was fine", niece Chloe Arnold said of her uncle, Fox News reported. He was in the country to attend his stepson's wedding.
Dozens of other tourists have reported severe sickness during visits to the resorts. He was staying at the Hard Rock Hotel & Casino in Punta Cana where he eventually died.
"People report food-borne illnesses but it's possible that they experienced some other type of contamination", said Patrick Quade, founder of iwaspoisoned.com, adding that he had consulted with scientists with regards to the findings.
Harrison's death certificate pegged the cause as pulmonary edema coupled with a heart attack.
Their deaths were all put down to heart attacks or respiratory failure.
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Nathaniel Holmes and Cynthia Day, in a file photo, were found dead in their room at the Grand Bahia Principe La Romana on May 30, 2019.
What was once a carefree decision on a Caribbean vacation - a trip to the Dominican Republic - has become something of a nightmare for Americans contemplating a trip to the island.
The FBI is assisting Dominican authorities on the ground with all six deaths.
Meanwhile, a DE woman named Tammy Lawrence-Daley said she was attacked in the Dominican Republic at another all-inclusive resort while she was vacationing with her husband and some friends. Within five days, three US tourists died in their rooms at hotels owned by the Bahia Principe Hotels and Resorts group, a different hotel chain than where McCoy and her husband stayed.
The FBI is sending experts to the Bahia Principe hotels where the latter three stayed to conduct the investigation.
The relatives of Robert Bell Wallace told Fox News on Sunday they chose to share the story of his death at the Hard Rock Hotel and Casino resort in light of the recent deaths of American tourists on the Caribbean island.
Another couple, Kaylunn Knull and Tom Schwander also reported of headaches abdominal cramps and diarrhea after encountering a strong smell of chemicals in the La Romana hotel in June 2018.