The FBI’s Jeffrey Sallet has taken on mobsters and terrorists.

He fled the dust cloud when the first tower fell on Sept. 11, 2001. He had nearly finished his fourth Boston Marathon when the bombs went off on April 15, 2013 — before he tossed on his finisher’s shirt and joined the manhunt for the bombers.

But as he prepares to take the helm of the FBI’s field office in Chicago, Sallet said there is one issue already keeping him up at night: This city’s ongoing struggle with gun violence.

“I’m doing my homework and making sure that I am engaged on that issue from the moment I hit the ground in Chicago,” Sallet told the Chicago Sun-Times.

Sallet is coming here from New Orleans, where he led the FBI’s field office for two years. He officially becomes Chicago’s special agent in charge on Nov. 6, assuming the job last held by Michael J. Anderson, who announced his retirement in August.

But Sallet takes on the job as the city continues to struggle with violent crime — and amid a difficult conversation about police reform.

Six months ago, Sallet joined other federal authorities in announcing they would not bring charges in the death of Alton Sterling, who was fatally shot by police in an incident caught on camera. The video sparked outrage in Baton Rouge.

Sallet said he also oversaw the FBI’s national response to similar incidents in Ferguson, Missouri, Baltimore and New York. He said such cases need to be looked at critically, and he insisted the FBI is “not the national shooting review board.”

“We have extreme faith and confidence in state and local law enforcement to investigate their shootings,” Sallet said.

Sallet joined the FBI in 1997. He has served as a supervisory special agent in the FBI’s La Cosa Nostra unit and also worked in New York. He took on Joseph Massino, the so-called “Last Don” who became the first-ever crime boss to cooperate with the feds.

Sallet also handled the investigation that led to the conviction of New England La Cosa Nostra boss Luigi “Baby Shacks” Manocchio.

“That basically took out the leadership of what was left of the New England mob,” said Rick DesLauriers, the former special agent in charge of the FBI in Boston.

DesLauriers said he was “extremely impressed” by Sallet’s leadership and promoted him shortly before the Boston Marathon bombing.

The day of that attack, Sallet said he had already run nearly 26 miles — and his wife and young children were waiting for him at the finish line — when the bombs went off.

Sallet made sure his family was safe, took a quick shower and went to work. But DesLauriers said Sallet was still “red and sweaty” from the race when he got to the office. And despite any exhaustion, he said Sallet “immersed himself” in the case.

“That shows you what kind of agent he was,” DesLauriers said.

The FBI tracked down the bombers, Dzhokhar and Tamerlan Tsarnaev, in roughly 104 hours. Surveillance video was key to its investigation. Sallet discussed it on the National Geographic Channel’s documentary, “Inside the Hunt for the Boston Bomber.”

“There’s this impression from ‘CSI’ that you solve everything in 10 minutes with video forensics,” Sallet said in the documentary. “But it’s just tenacious labor of looking at the video over and over and over again.”

That experience clearly stuck with Sallet when he took over the FBI office in New Orleans. The FBI installed temporary cameras to monitor Mardi Gras in 2016. Sallet also said it had “located and mapped every single camera in and around any part of the French Quarter, the parade routes and any other critical infrastructure.”

“Assume that you are being filmed wherever you are and whatever you’re doing,” Sallet told the public that year.

Chicago just undertook its own security review after this month’s mass shooting in Las Vegas, the deadliest in American history.

Days after the gunman opened fire on a country music festival from a room at Las Vegas’ Mandalay Bay Hotel and Casino, it was revealed he had previously booked rooms in Chicago overlooking Lollapalooza. The shooter never showed up here, though.

Sallet simply said, “we have to be prepared” for the new normal of mass violence. He added, “I’m certainly going to be working with the Chicago Police and all of our law enforcement partners.”

“The Chicago Police Department are second-to-none when it comes to a big city police department,” Sallet said.