Does Walmart have undercover security and is this what I encountered?

Tonight I went to my local Walmart. Granted I’m more of a Target person, but I made an exception. First a little background, my dad is a police officer, my mom works for the city, I’m 17 and work as a host at Stone Creek Dining Company, I am not a thief and I do not mix with a questionable crowd. I was in the men’s pajama section when I noticed a man, maybe mid 20s, torn jeans, black cap, very creeper-ish walking back and forth starring at me pretending to be on his phone. I was disturbed so I walked away. When I went to check out, I noticed him following me and being quite obvious about it. I was a little perturbed so I put down my items and headed for the door. He ran up to it! I was freaked out. So I went to head toward another exit, hoping I’d lose him and he just ran along side the other side of the cash-registers. Not cool! I went to the jewelry counted and told the woman a man was following me, she asked for a description and that’s when the man ran up to the other side of the counter! I was flipping out. I told her, he was right behind her and she said she didn’t know what to do. I looked like I hadn’t noticed and discretely called 911. I was on the phone with a dispatcher and headed toward the customer service desk to find a manager while the man continued to follow me. After reporting to a large man who worked at the store that I was being followed, and upon pointing out the stalker, the employee in question informed me that the man following me was their security. I was relieved and hung up with the dispatcher after apologizing for the confusion. I went to go address the "security officer" and tell him of the panic he had ensued and he started to run away. I chased him to the main isle in front of the cash- registers and demanded his attention telling him that I called 911 because I thought he was someone who was going to mug me. He just said, "Oh I wasn’t following you, I’m on break". Disgusted I started to walk away when I noticed him following me yet again. I asked a cashier if they had undercover security. The man told me, no, they did not. I was immediately back in a frenzy, I said then I need your real security because there is a man still following me, and after taking a glance at my stalker, the cashier said that, "they may have security like that". I asked him if that was one of the guards and he told me that it was and asked me why I would be followed by him in a manner that insinuated that I might be shoplifting. I was distraught at the entire situation, left my cart, and walked out of the store enraged. I do not know what to do. I’ve found a couple stories on the internet about being stalked in Walmart, but none with any real answers. I want to know if this is a regular policy of Walmart, and what I need to do to complain because I will never go back to that store after being treated the way I was. Terrified and revolted at it all,William