In his final weeks with the NYPD, Commissioner James O'Neill sat down with News 12 to reflect on his time with the department and as the city's top officer.

For the last 37 years, James O'Neill spent his days working to protect New York City. He announced last week that he was leaving the department to take a job with Visa.

"I have very mixed feelings, I do, almost 37 years is a long time," says O'Neill.

The Brooklyn-born commissioner started out as a transit officer in 1983. He says he never thought he would ascend to the top of the ranks. He became chief of the department over 30 years later in 2014.

"The Ferguson [Missouri] decision was the end of November 2014, and the [Eric] Garner decision was the next week. We had weeks of protests sometimes three or four-thousand people, I think one Saturday there were 30,000 people.

Then on Dec. 20, 2014, two NYPD officers - Rafael Ramos and Wenjian Liu - were assassinated in Bed-Stuy.

"That got close to bringing us to our knees. That really helped me learn that if we're going to make the city safe, if we're going to keep the cops safe, there's got to be real relationships built up through all five boroughs," says O'Neill. "They have to trust us and we have to trust them."

The violence led to neighborhood policing and the start of the neighborhood coordination officer program.

In 2016, O'Neill took over as police commissioner. On his first day in the role, the Chelsea bombing injured dozens in Manhattan.

"I said, uh, OK this didn't take too long to test me," says O'Neill.

Despite that, O'Neill says she never lost sight of the bigger picture -- safety. One way he handled that was implementing body cameras on all uniformed officers.

Over the summer, O'Neill made the controversial decision to fire officer Daniel Pantaleo in connection to the death of Eric Garner.

"I said it that day and I'll say it again, and I don't think it's all police officers, but I'm sure there were many police officers that weren't happy with that decision, but there are rules and regulations in the NYPD that have to be followed, and I have to look out for all 8.6 million New Yorkers," he says.

In recent months, mental health became a focus, with 10 NYPD officers taking their own lives in 10 months.

"It crushed us, it crushed me personally," says O'Neill. "To think that, you hear one, and then another and another and another. When's it going to stop? What are we going to do? We have to do it fast."

He insists the the NYPD is making changes, so far training peer support counselors and partnering with New York Presbyterian, but adds that one of the biggest challenges they're facing is the stigma.

As to why he resigned now, O'Neill says there was nothing that specifically impacted the timing.

"There was an opportunity for me ... I'm not sure that these opportunities are always going to be out there," says O'Neill. "Also excited about moving on to the next chapter of my life. You know, my mom is 88. Maybe I'll have the opportunity to see her a little more. I have two sons, maybe I'll get some time to spend with those guys."

As for his future in law enforcement, he's not ruling anything out, saying, "It's in my blood. I can't say. But if the opportunity presented itself down the line, I'd have to really think about it."

O'Neill's last day is Nov. 30, with Chief of Detectives Dermot Shea set to take over Dec. 1.