It took James O’Neill more than three decades as a cop to ascend to the top of the nation’s largest police department, but only a little more than day to get his first real test.

O’Neill’s first full day as New York City’s police commissioner ended with him racing to the scene of an explosion Saturday in the Manhattan’s bustling Chelsea neighborhood that injured 29 people. He immediately took charge of the investigation, offering the nation its first, up-close look at his no-nonsense, just-the-facts management style.

And less than 40 hours later, a suspect was behind bars, believed to be responsible for the blasts in both New York and earlier in a New Jersey shore town.

“It’s a pretty tough way to start in my new position,” O’Neill acknowledged Monday at a news conference detailing the capture of 28-year-old Ahmad Khan Rahami.

“But I was just so proud of what I saw that day,” he said. “The work that was done together, how it was done, all the agencies, the level of cooperation was impressive.”

The 58-year-old known to his colleagues as Jimmy Is a measured departure from the media-savvy style of his more political predecessor, William Bratton. In news conferences, O’Neill largely deferred to Mayor Bill de Blasio and his department chiefs, stuck mostly to what investigators knew and didn’t know, and didn’t even change expression, even when talking about the fast, successful arrest.

“I have to say it was absolutely a seamless transfer of leadership,” de Blasio said of the new commissioner. “He took over command of the situation on Saturday evening – was entirely on top of the action.”

If O’Neill sounds more like a police officer than a bureaucrat, it comes naturally. From his start as a transit patrolman in 1983, he worked his way up through the ranks, most recently serving as the 36,000-officer department’s top chief.

In fact, taking the civilian commissioner’s job was the first time in his career that he was no longer required to wear the NYPD uniform.

“It’s just that I’ve been wearing this uniform for almost 34 years. Now it’s really starting to hit me,” O’Neill told The Associated Press in an interview last week on the eve of his formal, official swearing-in Friday. A public ceremony Monday came just a few minutes before the news conference on Rahami’s arrest.

The Brooklyn-born O’Neill makes no secret of approaching the most powerful job in local law enforcement differently from Bratton, who cultivated an image as a crime-fighting innovator in stints running police departments in Boston, Los Angeles and two times in New York.

“If you talk to anyone who’s ever known me, they’d say we’re different people,” O’Neill said of Bratton, who is leaving to work as a private security executive. “I think my way’s a little different — not better, not worse. … I don’t need a big personality. I just do it one person at a time.”

He’s also open about a mid-career crisis that had the potential to put him on an early retirement track. It came in 2008, when, as the head of a narcotics unit, he was transferred amid allegations that informants were being paid with drugs instead of cash. Four narcotics investigators ended up facing criminal charges, and hundreds of criminal cases were affected, with prosecutors forced to dismiss charges or vacate convictions.

“I wasn’t happy about it,” O’Neill said about the situation. But by nature, he couldn’t leave.

“I thought about it, but I love being a cop,” he said. “I love the NYPD.”

O’Neill continued rising through the ranks until Bratton’s return, when the new commissioner tapped him as his successor.

He concedes the complexities of fighting conventional crime and protecting the city against terrorism are daunting. A wake-up call came when he saw the degree of outrage during protests amid the fallout from a grand jury’s decisions not to prosecute in the killings of unarmed black men in New York City and Missouri.

Before the wave of outrage, “Were we always loved? No,” he said. “But we were never vilified in that way.”

The reaction made him more convinced the NYPD needed to push forward with a neighborhood policing program designed to give patrolmen more time to walk around and mix with the communities that they police rather than staying in their cars and only responding to 911 calls.

His message at police roll calls was simple: “Remember why you became a cop and we’ll get through this.”

As an insider, O’Neill will have police officers’ trust, said Ed Mullins, president of the Sergeants Benevolent Association.

“The benefit of O’Neill is that he came up through the ranks, through the precincts. And there’s a bond with that that gets formed over time,” Mullins said. “I think the rank-and-file would like to see him succeed.”

Some activists, mindful of the NYPD’s sometimes-fractious relationships with minority communities, took a cautious approach.

“We’re prepared to hold O’Neill’s feet to the fire, just as we did with Bratton,” said Lumumba Akinwole-Bandele, a member of Communities United for Police Reform.

(AP)