Videos bring back happy memories of Mary Nielsen's two children."Teddy was just so sweet and loving. He was a mama's boy, you know," Nielsen said, "Emmy was exceptionally smart. She just had turned 5 in January, and you wouldn't have known it." Now these memories are all Nielsen has, after her two children were found dead in their father's home last month. "They had like a special bond, like, they were very, very close, and you could tell they were best friends," she said. Those two little best friends, 5-year-old Emily and 3-year-old Teddy were staying with their father, Adam Price, last month. Nielsen lives in Illinois. "Saturday rolls around, and I was like, it was like 6:30, seven o'clock and I was like, 'the kids haven't called yet,' and I was like, 'they didn't call last night, either,'" Nielsen said. According to Nielsen, a custody agreement required that the kids check in with her every day while visiting their dad."So I started calling him and blowing up his phone and texting him I'm like, 'even if you can't talk, like, I need to know the kids are safe,'" she said. Nielsen posted on Facebook, asking if anyone had seen Price and the kids.Meanwhile, police went to the house twice for welfare checks but say they had no cause to force their way in."I had a bad feeling in the pit of my stomach," Nielsen said. Nielsen's friend offered to go over to the home. She said the friend found the door unlocked, and inside, the bodies of Emily and Teddy."I had to pull over, I was bawling," Nielsen said. Price was gone. Authorities arrested him hours later in California. Nielsen calls her past relationship with him abusive and said her children were the only reason she survived."I mean, I was very suicidal for a very long time during the relationship. Abusive relationships, like destroy you," she said. Nielsen said she moved back in with her parents in Illinois to finish school and spend more time with her beloved kids. Now, as she mourns her beautiful, cheerful children, Nielsen wishes more would have been done to protect them."If someone had just listened to me when I said he was an unfit parent, they'd still be here, and it's still really hard," she said, "I just, the only thing that makes me feel like a tiny bit better is they don't ever have to see him again, but at the same time I'm missing them so so much." Price is charged with two felony counts of child abuse resulting in death. His next court appearance is scheduled for June 15.