The incident was caught on surveillance video.
Shelly Scott says her 13-year-old grandson was coming home from Markam Woods Middle School in Lake Mary, Florida on Wednesday when he was slapped in the face by the bus monitor.
"As adults, we have to be accountable for our actions and that was just not right on her behalf," said Scott.
According to the arrest report, 55-year-old Beverly Morton accidentally struck the boy as he was attempting to pull a book out of her hand. The boy's family says he says he was trying to stop the book from slipping out of her hands.
Investigators said surveillance video on the bus revealed Morton, "Slapped (him) with enough force that a sound was heard." The video was not able to be released to Channel 9 to in order protect the victim of alleged child abuse.
Scott once worked as a school bus monitor herself and said they're trained to handle these situations.
"Bus monitors are supposed to be there to protect our children. To keep things in line. Not to hurt them."
The Seminole County School District placed Morton on paid administrative leave. Scott said she wants Morton fired for good.
"I don't feel like she scared just my grandson by what she did to just him, these other kids witnessed that as well," said Scott.
Morton has worked for the district for 18 years.