Over the course of an eight-hour deposition, Florida surgeon Thomas Shaknovsky faced the same question again and again: Why did he remove a man’s liver instead of his spleen?

The disastrous August 2024 surgical error and death of Shaknovsky’s patient, 70-year-old William Bryan, on the operating table prompted Bryan’s widow to file a lawsuit last year and a grand jury to indict Shaknovsky on a manslaughter charge last month. He has pleaded not guilty.

Exactly what went wrong during the planned splenectomy has remained a mystery — especially since Shaknovsky has not spoken publicly about the case.

A deposition Shaknovsky gave in November as part of the lawsuit offers his first detailed, emotional account of the operation. Shaknovsky said there were unusual factors that made Bryan’s procedure more difficult. And he described the profound toll of losing a patient, saying he broke down in tears afterward.

“That was an incredibly unfortunate event that I regret deeply, and I’m forever traumatized by it and hurt by it,” he said, according to a transcript of the deposition shared with NBC News by attorney Joe Zarzaur, who represents Bryan’s widow, Beverly Bryan.

Wrong-site surgeries can occur “during difficult circumstances,” Shaknovsky said, which in this case included blood in Bryan’s abdomen and an enlarged colon obstructing Shaknovsky’s view of other organs.

Shaknovsky said that while he was trying to get a better view as the operation was underway, Bryan started bleeding profusely, causing his heart to stop. As the operating room team did chest compressions, Shaknovsky said, he desperately tried to find the source of the bleeding. It was during that chaotic time that he accidentally removed Bryan’s liver rather than his spleen.

Shaknovsky then instructed a nurse to label the organ he removed as a spleen — which typically weighs less than 15% of a liver.

“I can’t explain to you what it’s like for a surgeon to lose a patient on a table and how demoralizing it is and how devastating it is. And I couldn’t tell the difference because I was so upset,” Shaknovsky said of mixing up the organs.

“It’s a devastating thing, which I will have to live with the rest of my life,” he said in the transcript, which is about 400 pages long, “and I think about it every single day.”

Prosecutors have not offered a detailed timeline of how the surgery unfolded. A medical examiner determined Bryan died of “exsanguination,” or bleeding to death, and “surgical removal of the liver,” according to his death certificate.

Neither Shaknovsky nor his attorneys responded to a request for comment on his deposition. The lawsuit, which also names Shaknovsky’s former private practice, is ongoing. Shaknovsky and the practice have denied intentional wrongdoing in court filings.

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Bryan, a veteran from Muscle Shoals, Alabama, had been visiting Florida with his wife when he began experiencing pain on his left side, according to Beverly Bryan’s lawsuit. The couple went to Ascension Sacred Heart Emerald Coast in Miramar Beach, where, according to the lawsuit, Shaknovsky convinced them that Bryan urgently needed a splenectomy, despite the couple’s wanting to return home to Alabama.

A spokesperson for Ascension Sacred Heart Emerald Coast, the hospital where the operation took place, said in a statement last month that Shaknovsky was not employed directly by the health system and that he has not practiced at any of its facilities since August 2024. The statement added that safety is the hospital’s top priority.

In his deposition, Shaknovsky said that he had met briefly with Bryan several times in the days leading up to the surgery and that they had connected over a shared love of Alabama college football. He described praying with the Bryans before the operation began.

Once they were in the operating room, however, the procedure did not go as planned. Shaknovsky said that Bryan began bleeding heavily and that he could not figure out where the blood was coming from.

“It was like a overflown sink that’s clogged up, and I am looking for a fork at the bottom, trying to feel and find the bleed, and I was not able to do so,” he said, according to the deposition. “After 20 minutes of struggling, desperately trying to save his life, that’s when the wrong-site event took place.”