"There is no possible way; she would not do that," Hicks' mother, Robbin Hicks, 40, told Illinois newspaper The Telegraph. "I don't believe that. I'm not letting this rest, especially with her being shot in the side of the head. I want justice for her. She could have made it. This mother is not going to let this one go."
Robbin Hicks told the paper that her daughter "had problems, but wasn't a bad kid."
"She got into drugs and alcohol," Robbin Hicks said. "We did everything in our power, taking her to rehab in Carbondale, but she ran away after two weeks."
She said her daughter was diagnosed with bipolar disorder.
Hicks told the paper she also took her daughter to facilities for mental health treatment in the past few weeks.
"She was very smart, a good kid, feisty," Hicks told the paper. "She was bubbly, loved to dance and sing. She was always singing about something."
The investigation into Hicks' death is ongoing.