He Was Just the I.T. Guy. Then He Got Caught in the Trump Documents Case.

One day in June of last year, at a time when federal investigators were demanding security footage from former President Donald J. Trump’s Mar-a-Lago estate, Yuscil Taveras shared an explosive secret.

Mr. Taveras, who ran Mar-a-Lago’s technology department from a cramped work space in the basement of the sprawling Florida property, confided in an office mate that another colleague had just asked him, at Mr. Trump’s request, to delete the footage that investigators were seeking.

Mr. Taveras later repeated that story to at least two more colleagues, who in turn shared it with others, according to people with knowledge of the matter. Before long, the story had ricocheted around the grounds of Mr. Trump’s gold-adorned private club and up the chain of command at Trump Tower in Manhattan, prompting Mr. Taveras’s superiors in New York to warn against deleting the tapes.

But by then, Mr. Taveras had already balked at Mr. Trump’s request. Looking to steer clear of the investigation into whether the former president was hoarding classified documents at Mar-a-Lago, he told one colleague that he was unwilling to cross a line and potentially go to prison, according to another person with knowledge of the conversation.

Still, when he was summoned before a grand jury this spring, Mr. Taveras did not fully recount the incident. Only after prosecutors subsequently threatened to charge him for failing to tell all that he knew did Mr. Taveras shift course to become a potentially important witness in the case.

Facing indictment this summer, Mr. Taveras replaced his lawyer, who was being paid by Mr. Trump’s political action committee and also represented one of the former president’s co-defendants. Mr. Taveras then returned to the grand jury and offered a more detailed version of events, recounting how he had been asked to delete the surveillance footage. In exchange, prosecutors agreed not to charge him.

This account of Mr. Taveras’s turnabout, drawn from court records and interviews with nearly a dozen people who know him and are involved in the matter, reveals new details of the critical if at first reluctant role he played in helping investigators develop evidence that Mr. Trump and two aides allegedly plotted to destroy security footage showing boxes of classified materials being shuttled in and out of a storage room at Mar-a-Lago.

Prosecutors have thrust the once-obscure Mr. Taveras, a 45-year-old computer whiz with a wife and two children, into the delicate position of being both Mr. Trump’s employee — he continues to work at Mar-a-Lago — and a witness against him.

Mr. Taveras is expected to testify against the former president as well as two of Mr. Trump’s employees, Walt Nauta and Carlos De Oliveira, all of whom were charged with a conspiracy to obstruct the government’s investigation. It was Mr. De Oliveira who asked Mr. Taveras to delete the footage, according to prosecutors.

The sequence of events surrounding the surveillance tapes, as laid out by prosecutors in the indictment and in interviews, fits a common pattern over many years for those in Mr. Trump’s orbit, with some aides rushing to carry out his wishes and others seeking to rein him in to avert legal and political risks.

The case has also made Mr. Taveras something of a singular figure in Mr. Trump’s world: He is the first Trump employee facing prosecution in the classified documents case known to have signed a cooperation agreement to avoid indictment.

His situation stands in contrast to a number of people entangled in the Fulton County, Ga., investigation into efforts to reverse Joseph R. Biden Jr.’s victory in the state, many of whom have found themselves on their own, battling charges or tens of thousands of dollars in legal fees as witnesses.

Six Trump associates were also named as unindicted co-conspirators in the federal case brought by the special counsel, Jack Smith, accusing Mr. Trump of plotting to overturn the 2020 election and thwart the lawful transfer of presidential power.

The degree to which other defendants or witnesses might turn against Mr. Trump in any of the cases remains to be seen.

And there is some possibility that Mr. Taveras’s testimony could be excluded from the classified documents case Mr. Smith has brought against Mr. Trump, Mr. Nauta and Mr. De Oliveira. Last month, Mr. Taveras’s former lawyer, Stanley Woodward Jr., asked Judge Aileen M. Cannon, who is overseeing the matter in Fort Pierce, Fla., to strike Mr. Taveras’s account from the record, complaining that it had been improperly obtained through “potential grand jury abuse.”

Mr. Woodward, who represents Mr. Nauta, argued that after indictments are issued, grand jury proceedings cannot be used “as a subterfuge to place pressure on a witness in order to obtain information,” suggesting that had happened to Mr. Taveras. Judge Cannon has not yet ruled on his request, which prosecutors are fighting.

A spokesman for Mr. Trump declined to comment.

According to people familiar with his role at Mar-a-Lago, Mr. Taveras rarely had contact with Mr. Trump. Because of that, people around Mr. Trump profess not to be particularly concerned about the threat that Mr. Taveras’s testimony might represent to the former president despite his apparently damning secondhand account of Mr. Trump’s wish to have the security footage deleted.

Mr. Trump, Mr. Nauta and Mr. De Oliveira have all denied wrongdoing and pleaded not guilty. Their trial is scheduled to begin in May of next year.

For now, Mr. Taveras appears to be keeping a low profile, and has no plans to leave his job at Mar-a-Lago, according to people with knowledge of his situation.

A native New Yorker with a love of music, Mr. Taveras once worked as a D.J. but came to focus on computers. He has worked for Mr. Trump for 13 years, first in New York before eventually earning a promotion, according to a person close to him. His new position running the tech support department at Mar-a-Lago brought him and his family to Florida in August 2019. They live in a modest house in a gated community.

Mr. Taveras’s path from obscurity to the heart of a federal case against a former president began on a Friday afternoon in late June of last year. That day, prosecutors issued a subpoena to the Trump Organization for months of security footage from around Mar-a-Lago.

Soon after, Mr. Nauta, Mr. Trump’s personal assistant, and Mr. De Oliveira, Mar-a-Lago’s property manager, contacted Mr. Taveras.

“Hey bro you around this weekend,” Mr. Nauta texted to Mr. Taveras, who was indeed in the area entertaining family visiting from New York. Mr. De Oliveira then texted Mr. Taveras, telling him that Mr. Nauta “needs you for something.”

What they needed became apparent a few days later, when Mr. De Oliveira walked into the I.T. department’s basement work space, steps from the club’s accounting department and other offices, and asked to speak with Mr. Taveras somewhere more private.

According to the indictment, which does not name Mr. Taveras but refers to him as “Trump Employee 4,” Mr. De Oliveira led him through a basement tunnel to a small room known as an “audio closet,” where Mr. De Oliveira delivered a message from Mr. Trump: “the boss” wanted the footage deleted. Mr. Taveras rebuffed the request, prosecutors said in the indictment, but Mr. De Oliveira raised it again.

“What are we going to do?” he asked Mr. Taveras.

Soon after returning to his office, Mr. Taveras confided in a colleague, Renzo Nivar, what had just happened, according to people with knowledge of what took place. And within days, Mr. Taveras relayed the story to a superior in Trump Tower.

One executive in New York, Matthew Calamari Jr., the Trump Organization’s corporate director of security, apparently became alarmed, according to people with knowledge of the matter. He alerted the company’s legal department, prompting a senior lawyer at the company to deliver a stern warning not to delete anything.

Ultimately, the company handed over the footage, and the indictment does not accuse anyone of deleting any tapes.

Yet Mr. Taveras’s testimony could be crucial to proving that Mr. Trump, Mr. Nauta and Mr. De Oliveira were conspiring to obstruct the investigation.

At one point after the subpoena for the footage had been issued, a worker drained the pool at the club, and it flooded the room housing the servers storing the surveillance footage, according to a person with knowledge of what took place.

It was unclear whether that was intentional, and the servers were not damaged, but the timing of the flooding raised enough concern that Mr. Calamari ordered the servers moved to another location, according to the person with knowledge of the events. Mr. Taveras was aware they were moved, the person said.

Prosecutors could also call on Mr. Nivar and Mr. Calamari to testify at trial.

And they could seek testimony from a former Mar-a-Lago employee referred to in the indictment as “Trump Employee 5.” In June of last year, the indictment said, that employee discussed the footage with Mr. De Oliveira, who told him that he wanted to ask Mr. Taveras how long Mar-a-Lago stored its surveillance tapes.