Transcript for Mom on Crusade After Catching Nanny Shaking Her Daughter
Reporter: Raising a child can be tough and when both parents work, sometimes a nanny is the only answer. Open wide! But do you really know who is taking care of your child? Especially when nannies have been caught on camera, doing the unthinkable. Nightmare nannies, accused of violating a most sacred trust, back in the headlines, just last month. You see these horror stories on TV and it's like a surreal feeling when it happens to you. Reporter: In Springdale, Arkansas, in the shadow of the ozarks, one mother is on a crusade to stop nightmare nannies before they ever walk through the front door. Do you ever think about, I hired a monster? Yes. Reporter: It began when Whitney Matney and her husband Chris were looking for a nanny for their daughter raylee while Whitney attended law school. A former high school classmate, Melissa Medema answered the callout. Someone Whitney thought she could trust, but still -- you ran background checks. Mm-hmm. Reporter: Did you call references? One raved about her. Raylee seemed to really take to her. So I ended up hiring her. Reporter: But almost immediately, raylee started acting strangely. When Melissa showed up raylee would run to either my husband Chris or, or I and cling to us and scream. So I put up this camera. Reporter: And after just the first day recording, Whitney knew the nanny cam captured something terrible, before she watched a frame of video. I got home and I saw the camera sitting there. Facing the wall. My heart just leapt in my throat. And I grabbed the camera, and I set my computer up. Reporter: To her horror, the camera caught Melissa spanking, and then violently shaking her 11-month-old baby girl. How hard is it to see that? It's very hard. Reporter: Frankly, hard for me to watch it too. And you can see raylee screaming. It didn't sink it at first, I just, I couldn't believe it. You know? Reporter: Melissa would later claim they were "Just playing," but how do you explain this? Right after the shaking, Melissa spots the camera, walks over to it and stares into the lens, posing for a chillingly calm and candid selfie before turning it toward the wall. I was filled with rage and fury, like I've never been before. Reporter: After watching the video, frantic, Whitney calls police and rushes her daughter to the emergency room. The police officer said, I think if you hadn't caught this when you did, you would have come home and had no baby anymore. Reporter: Luckily, raylee is physically okay. And Whitney realized her daughter's behavioral changes were actually warning signs. I should have caught it sooner. Everything fits now. Reporter: Incredibly, two days later Melissa shows up again for work, and police are waiting to bring her in. Peeking through a window, Whitney records that moment, assuring little raylee, she's safe now. She's not coming in, baby. You really can't do too much to confirm that you are hiring the right person. Reporter: In home child care expert Susan tokoyer says you need to do diligent background checks and digital digging. But even in this age of nanny cams, some things need to be done old school. Dropping in during the day is a great idea. Walking in the front door when she is not expecting you. Reporter: Now here's where things get really scary. Because raylee wasn't physically injured, Melissa was allowed to plead to endangering the welfare of a minor, the lowest level felony charge, and after three years' probation she could have her record cleared. If this monster can walk around and have no ramifications, it's just beyond insane. Reporter: Now you'd think in this digital age, nightmare nannies would be branded for life, but ironically it's something the web lacks that may allow their past to stay under the radar. So there's not a national registry for child abusers? Correct. Reporter: That's right, aside from sex offenders, there's no public online registry of child abusers in this country. Whitney, now a mom on a mission, to change that. In 2015, we're going to send out a bill. Arkansas will be the first state to have one, if it passes. Anybody who has been criminally convicted, they need to be listed out there for everyone to see. Reporter: And what does Melissa have to say about all of this? We tracked her down at this Springdale, Arkansas, apartment complex. Can you tell us what happened in that video Melissa? We're here to get your side of the story. It seems Melissa isn't in the mood for another close-up. Do you think that was child abuse? Will you nanny for another family? Were you trying to harm raylee? Go away. Reporter: Shortly after our visit, she gave me a call to let us know exactly how she was feeling. Paula, this is Melissa media and you came to my residence this morning. First of all I do not appreciate that. Do not come back to my residence, do not contact me, and that goes for all ABC news reporters. We showed Whitney the footage of Melissa scurrying away from our cameras. It makes me sick to my stomach. Because she was horrible to my child. Reporter: The good news? Raylee just turned three and seems to have put that babyhood trauma behind her. How is she doing? She's great. She is energetic, sassy. She's always smiling. Reporter: She's learning that even scary stories have valuable lessons. What to do if the monster of the woods comes calling on a dark and stormy night. Lock the door. Wow. Have you ever had a nightmare nanny? Let us know, use #abc2020. When we come
This transcript has been automatically generated and may not be 100% accurate.