(Meredith) -- Cellphone video shows a 9-year-old boy screaming for help as his mother picks him up by the arms and throws him to the ground at an Iowa gas station.
Two witnesses, Michael Lomax and his fiancé, Arekya Quinn, said they intervened when they heard the child yelling inside the Quick Trip in Des Moines on Sunday.
"The child is screaming for his life. I'm like, 'Unhand him! Let him go!'" Lomax told CBS affiliate station KCCI-TV. "I think I might have grabbed [the mom] or something to get her off of him."
"She smacked his face, and that's when I came in, and I pushed her," Quinn added. "Like, get off of him. You don't do that to a child."
Another video shows the mom, identified as Rejanie Morris, punching Quinn in the back of the head after Quinn tried to help the boy. Quinn fights back and takes Morris to the ground, hitting her several times.
Des Moines Police Sgt. Paul Parizek said when officers arrived, Morris was "screaming, yelling, and throwing property."
"Once we were able to get her in custody and she calmed down a little bit, what we learned was that prior to our arrival, she had actually assaulted her child twice," said Parizek.
"To see it on video is horrifying," he continued. "And you do become concerned about if she is going to do this in a public place, what kind of things are going on at home."
Morris was arrested and charged with child endangerment and two counts of assault. The assault charges are related to the physical altercation she had with Quinn and Lomax.
Police said the boy, who has autism, was placed into the custody of Iowa's Department of Human Services.