In the first installment of CNBC Make It's new series HR Confidential, a New York-based human resources professional with nearly five years of experience tells Ruth Umoh about the shocking allegations she uncovered when she fired a manager due to poor performance. The below is told in the HR pro's own words, and has been edited for length and clarity.

The scenario:

I worked in human resources for a [retail] company where I covered HR for corporate, their retail stores and warehouses. The company's COO and I had to fire our web store warehouse manager due to poor performance and ineffective management. She was very upset, but she accepted the termination. Before she left, she said to us, "I agree to some of the reasons I'm being let go. But I'm going to say it's really hard for me that I'm being held to this standard when you have all this stuff going on under your nose that's going unpunished." She then began to unleash a list of ongoing misconduct: This person is sleeping with this person at work, and they know where to stand to hide from the cameras.

These people are dealing drugs, this is where they hide it, and this is when they do it.

At work, you can always tell when they're high.

These people are using the money that goes to buy snacks for the office and pocketing some of it and taking the groceries home to their families.

It made me feel like a failure at my job. Anonymous HR manager

We sat there. Usually, we take accusations like this with a grain of salt. However, there was something that felt so genuine about her story. It wasn't as if she was out to get these people in trouble. She simply felt hurt that she was being held to a certain standard with all of this going on. She was just honestly sharing her experiences. Emotionally, my jaw was dropped and I wondered how we were unaware about any of this happening. It made me feel like I was a failure at my job. Obviously, we couldn't show that we were in shock so we simply said, "Thank you very much for sharing." The minute she walked out, the COO and I just looked at each other incredulously. It was as if someone just dumped everything on us. Most shocking of all, a lot of the claims had to do with the person we were going to promote for her position.

Most shocking of all, a lot of the claims had to do with the person we were going to promote for her position. Anonymous HR manager

Although we had a few more terminations that we were planning on doing that day as well as general meetings, we ended up leaving the New Jersey office right after receiving this information. We were in such shock and had to regroup, get back to the corporate office in New York and notify the CEO immediately.

The solution:

We investigated, and almost all of her claims were true. There were two managers who were coming in early, clocking in and having sex in the warehouse. They stood in a spot where they couldn't be seen by the camera. Another person was selling drugs, and another person was getting high. Some people were stealing groceries while others were stealing products. As a result, we ended up firing quite a few people. We also made a presentation to the whole warehouse reminding them of our drug-free policy. We debated implementing drug testing but ultimately decided against it. We did, however, want to scare them, so we reminded them that we're able to and have a legal right to administer drug tests. I would not say that was even all that effective. I think most of them were just kind of laughing at us as we were doing it. With that being said, it was the route that we chose. One of the two people who were accused of sleeping together did get fired because of that, along with other issues. The second person who was having sex in the office was still promoted into the now-terminated manager's position. However, we put a lot of controls on him and continued to recruit for a replacement down the line. We also spoke with a warehouse manager who had been accused of drug use. We said to him, "Listen, we're not coming to you as an employer, we're coming to you as two people who care about you. What's going on? Let's be smart here.'" There are some questions about whether even that approach was appropriate. However, that's what we chose to do. We also put different things in place to, hopefully, put a little fear in them, for lack of a better word. When workers went out to get groceries, we had a whole system of checking into the bag. We ended up putting a logistics coordinator in the warehouse who was a real rule-stickler. Just having the presence of that employee put a little pressure on them. Overall, it was more just about increasing the feeling that they were being watched.

The lesson:

As awful as these examples are, they're apparently quite common in warehouses. There's a real warehouse culture that needs to be addressed, which was a big educational moment for me. Obviously, as an employer, I'm not going to say any of these behaviors are okay. But I also understand that these people are coming from a very low-income area. They're in jobs that are not necessarily as stimulating. And they are groups that live close to each other so they are probably socializing outside of work. Understanding the population better was a big learning experience for me. The fact that all this was going on without our knowledge showed us how much more we need to be involved. My office was in Manhattan, and this warehouse was located in New Jersey. It showed us how much we need to be there, we need to be present, we need to visit more often and they need to feel like we're watching. And similarly, it illustrated the importance of having a strong manager in place. You need someone who's overseeing things and who you can trust isn't going to let this type of behavior go down. After all, a lot of these claims were about the warehouse manager, too.

The fact that all this was going on without our knowledge showed us how much more we need to be involved. Anonymous HR manager