Video captured aboard an Ohio school bus shows the driver repeatedly screaming at a 12-year-old student, calling him a “fat crybaby,” and threatening to physically injure his father.

The incident happened on May 1, 2017, aboard a Dayton Public Schools bus driven by Demetrius Williams. In a shouting match that lasted approximately an hour, Williams can be heard berating 12-year-old Christopher Wilson, telling him repeatedly to “shut up and be quiet.” Christopher was on the school bus with his brothers.

When Christopher talks back, the driver taunts him, repeatedly calling him a cry baby and telling him “you ain’t gonna do nothing.”

In an interview with CNN, the boy’s father, Christopher Wilson Sr., said he was baffled by the treatment of his son.

“To do that to a kid is just crazy,” he said.

According to Christopher Wilson Sr., the incident started before the bus left school property, when the driver tried to confiscate his son’s cellphone. A principal boarded the bus to calm the situation, but once the bus left, Williams began berating Christopher.

At another point during the ride, Christopher phoned his father. Christopher Wilson Sr. told CNN that he could hear the bus driver’s voice while he was on the phone with his son.

“All I heard him say was, ‘That’s all right, tell your dad to meet me at the bus stop, I’ll beat his a—too.’”

But Williams actually drives past the bus stop. In the video, Christopher Wilson Sr.’s red truck can be seen trailing the bus on the left side.

Chris Sr. said he chased the bus for blocks, eventually cutting it off. However, the bus driver appears to refuse to let Chris and his brothers off the bus.

Chris Sr. said he ran to the back of the bus and opened the emergency hatch and “got my kids off.”

In a statement, Dayton Public Schools said that Williams “chose to resign effective May 22.”

It went on to say that “Dayton Public Schools does not tolerate any inappropriate actions by our employees.”

The school district superintendent said Williams would have been fired if he hadn’t resigned.