Pig-heart transplant recipient David Bennett, 57, has died, according to the Associated Press.

No precise cause of death has been given by his doctors at the University of Maryland Medical Center, where he had been recovering from his groundbreaking surgery, although they did report that he had been failing for several days.

The breakthrough surgery took place January 7. Such cross-species transplants, known as xenotransplantation, had been tried before, but all had failed quite quickly, due to rejection. This time a gene-edited pig heart was used, as well as anti-rejection measures.

At first, the operation was a success, and he did survive significantly longer than others who had undergone such procedures before.

Once it became clear that he was failing, Bennett was put on palliative care and he and his family had a chance to say goodbye.

“We are devastated by the loss of Mr. Bennett. He proved to be a brave and noble patient who fought all the way to the end. We extend our sincerest condolences to his family,” Dr. Bartley P. Griffith, who performed the transplant, said in a statement.

Dr, Muhammad M. Mohiuddin, professor of surgery and scientific director of the Cardiac Xenotransplantation Program at UMSOM, noted that much valuable insight was gained from Bennett's brave efforts. “We are grateful to Mr. Bennett for his unique and historic role in helping to contribute to a vast array of knowledge in the field of xenotransplantation,” he said.

Bennett was out of options when he came to the University of Maryland Medical Center for the procedure in January, HCB News reported at the time.

“It was either die or do this transplant. I want to live. I know it's a shot in the dark, but it's my last choice,” he said the day before the historic surgery would put a genetically-modified pig heart into his chest.

The surgery is the next step in “solving the organ shortage crisis,” Griffith noted at the time.

Nearly 110,000 Americans are now awaiting a transplant, and over 6,000 patients die each year before they can have one of the lifesaving procedures.

The organ used in Bennett's transplant, dubbed a UHeart, came from United Therapeutics subsidiary Revivicor.

Bennett's son, David Bennett Jr., expressed his and his family's gratitude in a statement, according to the Baltimore Sun.

He noted that, “up until the end, my father wanted to continue fighting to preserve his life and spend more time with his beloved family, including his two sisters, his two children, and his five grandchildren, and his cherished dog Lucky.

“We were able to spend some precious weeks together while he recovered from the transplant surgery, weeks we would not have had without this miraculous effort.”

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