The investigator in charge of the criminal case that led to the conviction of former Assembly Speaker Sheldon Silver has agreed to become first deputy commissioner of the Suffolk County Police Department, officials said Thursday.

In another sweeping change in the department’s top brass, Suffolk County Executive Steve Bellone said he has appointed John Barry, a criminal investigator at the U.S. attorney’s office for the Southern District, to become second in command of more than 2,400 sworn personnel.

“John Barry has an outstanding police and law enforcement background and will help restore a strong working relationship with our federal partners,” Bellone said on Thursday, adding that he has appointed “the right team to deal with issues we are confronting at the time.”

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Barry, 46, on Thursday has already began working with newly appointed Deputy Police Commissioner Tim Sini, Bellone’s pick for police commissioner pending county lawmaker approval. Sini said Barry has agreed to volunteer two to three days per week at police headquarters in Yaphank.

The leadership changes began shortly after former Chief of Department James Burke resigned on Oct. 27 as federal prosecutors in New York’s Eastern District intensified a grand jury probe into the circumstances surrounding the December 2012 arrest of Christopher Loeb of Smithtown. Newsday first reported Loeb’s arrest in February 2013 and federal officials launched an investigation of Burke that year to determine if he had violated Loeb’s civil rights but the case seemed to lay dormant until Burke’s sudden resignation.

As a criminal investigator for the U.S. attorney’s office, Barry, a lifelong Suffolk resident, said he has worked on his share of high-profile cases.

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Barry handled the case of former Bronx state Assemblyman Eric Stevenson who in 2014 was sentenced to 3 years in prison for taking bribes. He also worked on the federal corruption case against former State Senate leader Dean Skelos and his son Adam, who are currently on trial.

Most recently, Barry was the lead investigator on the Silver case, which ended with Silver being convicted this week of federal corruption charges, including extortion, bribery and money-laundering.

Sini is a former federal prosecutor who worked with Barry in the Southern District in Manhattan. Bellone announced Sini’s appointment last week a day after outgoing Police Commissioner Edward Webber announced his plans to retire next year.

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Barry said he’s leaving Manhattan and coming to Suffolk County: “Listen, this is where I live. I mean I’m so excited to come out here and work with all these law enforcement [agencies] and civilians and the police department and make the place that I live in, try to make it a better place.”

Since he began last week, Sini said he has worked closely with top brass to focus on what he calls a “top to bottom assessment.” He said he is already conducting interviews, asking for resumes and pulling internal affairs files.

Sini said he has found “a deep pool of talent” in the department. However, he said, “this department needs people with fresh perspectives and so in that vein I’ve recruited the latest addition which is John Barry.”