Mayor Megan Barry admitted Wednesday to an extramarital affair with a Metro police sergeant who had been assigned to protect her.

Still, in an exclusive interview with NewsChannel 5 Investigates, Barry insisted that she has not misused taxpayer funds as part of the relationship with Metro Police Sergeant Rob Forrest.

Forrest unexpectedly retired Tuesday after 31 years with the Metro Nashville Police Department.

"I'm very embarrassed, and I'm deeply ashamed, and I'm very sorry," Barry said. "The affair was between two middle-aged consenting adults, and it was a mistake to do this. And I am deeply sorry."

She added, "I know God forgives, but the people of Nashville don't have to -- and I also want to ask for their forgiveness."

Barry's admission came just days after NewsChannel 5 Investigates began inquiring about her use of taxpayer money.

The 54-year-old mayor said the relationship with the 58-year-old sergeant began shortly after her election in September 2015.

Special Section:

City Hall Scandal

We asked, "When it comes to the city of Nashville, you were Sergeant Forrest's boss. Why did you not say, at some point, if I am going to have this relationship, he needs to be removed from my detail?"

"That was a mistake, and I should have," Barry answered.

"So that was failure as the mayor?" we asked.

"That was a failure from a personal perspective to say this is something that is happening and I should remedy this," she continued. "What I should have done was -- not remedy him being a part of my security detail. I should have owned up and not had the affair."

During 2017, travel records show Forrest traveled with the mayor to San Francisco, Salt Lake City, Denver, Washington several times, as well as New York.

In September, he flew with her to Athens, Greece.

The next month, he traveled to Paris all, at taxpayer expense.

NewsChannel 5 Investigates asked, "Were all of those legitimate business trips?"

"Absolutely -- every single one of them," she answered. "And if it hadn't been Sergeant Forrest who would have been traveling with me as detail, there would have been other detail traveling with me. The detail security policy is set by the police department. They say I have to travel with security."

In fact, Forrest provided protection for former Mayors Bill Purcell and Karl Dean.

He averaged $34,000 a year in overtime for the last three years of Dean's term.

But after Barry took office, Forrest's overtime pay increased to just below $60,000 in fiscal year 2015-16.

The next year, that increased to more than $75,000, bringing his total pay to $157,187 for fiscal year 2016-17.

Metro Police spokesperson Don Aaron explained that "Mayor Barry has kept a daunting schedule since her election."

"The overtime," Aaron added, "is a reflection of that morning to night AND weekend schedule."

NewsChannel 5 Investigates asked Barry, "Some people will look at that and say that taxpayers are paying for this relationship. What would you say to that?"

"What I think what this reflects," she responded, "is the policy that the police have about making sure that when I am working that I have detail. I don't think it's a secret that I do work a lot and I do have a pretty aggressive schedule."

We asked, "Was he getting paid by taxpayes at any point when you all were having your personal time?"

"No," she insisted.

So how can taxpayers know that all of that overtime was completely legitimate?

Barry responded, "I think that the records will show that, if you look at my schedule versus his overtime, I think you will see that my schedule reflects that I was out there working."

Forrest was also there the day that Barry and her husband Bruce joined Nashville in mourning the death of her son Max.

But Max's death, she says, helps her keep this moment in perspective.

NewsChannel 5 Investigates noted, "There may be some people who say, she cannot govern, she must resign. What do you say to them?"

"No," she insisted.

"This is a bad day. I am going to have a lot more days coming. I've already had my worst day. And I know the difference between a mistake and a tragedy.

"This is a mistake. And I think that we've been able to show in this administration over the last two years that we've done a lot of really good things -- and that's going to continue to be my focus."

As for her future with her husband, Barry says that's for them to figure out.

"Bruce and I have a lot to work through -- and we are working through it," she said.

"I'm really blessed that I have a husband who is supportive of me, who has been there for me. We've been through a lot together. And this is something that, personally, we are going to work through."

Shortly after 6 p.m. Wednesday, Forrest issued a letter from his attorney releasing the following statement:

"For over 31 years I have been honored to serve in the Metropolitan Nashville Police Department. I devoted 14 years of that time supervising the mayor's protective detail during three administrations.

I deeply regret that my professional relationship with Mayor Barry turned into a personal one. This has caused great pain for my wife, my family, friends and colleagues. At no time did I ever violate my oath as a police officer or engage in actions that would abuse the public trust.

I have recently retired from the police department. I hope that the media and public respect my privacy and that of my family as I seek to rebuild the trust of the ones I love the most."

Mayor Barry addressed the media and the public about the affair in a press conference Wednesday evening.