BOSTON – The head of the FBI’s Boston office, one of the main law enforcement figures during the Boston Marathon bombing investigation, announced Tuesday that he’s stepping down to take a private-sector job.

Richard DesLauriers, who’s been special agent in charge of the office since July 2010, said he will leave next month after more than 26 years with the FBI. He said he has accepted a position as vice-president of corporate security with Penske Corp., a transportation services company, in Bloomfield Hills, Mich.

In an interview Tuesday, DesLauriers said he is most proud of his role in the apprehension of reputed mobster and longtime fugitive James “Whitey” Bulger; the arrests of two Boston-area Russian sleeper agents; the arrests and convictions of a man charged with conspiring to help al-Qaida and a man accused in a plot to fly remote-controlled model planes packed with explosives into the Pentagon and the U.S. Capitol; and the investigation into the deadly Boston Marathon bombing.

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DesLauriers was one of the main faces of law enforcement during the intense, five-day manhunt that led to the capture of the sole surviving suspect following the April 15 marathon bombing, which killed three people.

DesLauriers, 53, four years younger than the mandatory retirement age for FBI agents, said he first learned of the Penske job in March but delayed his decision because of the bombing investigation.

“My time was coming down the pike sooner or later, so this was a good time to pursue an opportunity with a real world-class organization in the private sector,” he said.

Before moving to Boston, DesLauriers worked for the FBI in New York and Washington, earning broad experience in counterintelligence work. As special agent in charge of the Boston office, he oversaw the FBI in Massachusetts, Maine, New Hampshire and Rhode Island.

After arriving in Boston, DesLauriers said he would have a “laser-like focus” on the search for Bulger and the investigation into the 1990 Isabella Stewart Gardner Museum art heist, the largest art heist in U.S. history.

His first goal was reached when Bulger was captured in Santa Monica, Calif., in 2011, after more than 16 years on the run. Bulger, 83, is accused of participating in 19 murders during the 1970s and ’80s but maintains his innocence. Opening statements in Bulger’s trial are scheduled Wednesday.

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The Gardner museum heist remains unsolved more than 23 years after two thieves disguised as police officers stole more than $500 million worth of art, but DesLauriers said the FBI had made significant progress.

“I certainly was hoping to recover that art prior to my departure,” he said.