"I immediately wanted to cry, I was so shocked, like how could this even happen," Tracy Ripley, the victim's granddaughter, told KPNX. "You are the one responsible for caring for her and that's how you treat her? It just makes me sick."
Officials from the facility said they immediately suspended Biamushinga, KNXV reported. She was later fired, Ripley told KPNX.
Ripley said the surveillance video showed her grandmother asking a caretaker to put her footrest down, the television station reported.
"She was unable to do that for herself and they were not listening to her," Ripley told KPNX.
Ripley said it appeared her grandmother was becoming agitated.
"She threw her water on the caregiver and then threw the cup off to the side and the caregiver hit grandma on the way to picking up the cup and then with the cup as she was leaving the room," Ripley told KPNX. "With Grandma and the dementia, she reminds me a lot of a toddler. I have a toddler and that's exactly -- you know, he acts like that. She acts like that.
"You don’t retaliate. You don’t hit them.”