HENDERSONVILLE, Tenn. -- A Sumner County family has filed a lawsuit after a school bus driver left their 7-year-old son in a parked bus for five hours with the engine running.

Video: Child Left On Bus; Mom Sues School Board

"They're unforgiveable mistakes (the bus driver) made," said mother Julie Vickers.

The child, Esaiah Vickers, had fallen asleep in the back of the bus on March 31. The driver, Robin Chandler, parked the bus at the school's maintenance garage with its engine running. Chandler said she didn't notice the child was still onboard.

"He was in tears when I got him off the bus," said Julie Vickers.

Esaiah woke up when the bus ran out of gas and an alarm went off.

The alarm is designed to go off when a bus is turned off, so that the driver remembers to make sure there are no kids left on board. Because she never turned off the bus, the alarm didn't sound until the bus ran out of fuel. Once the child woke up, he got out and looked for help.

"I got off the bus and was wandering around the building and I finally found somebody," said Esaiah Vickers.

His mother said Esaiah suffered from carbon monoxide poisoning and was tired for days.

"I could have been burying one of my children because of that mistake," said Julie Vickers.

The family has filed suit against the Sumner County Board of Education and the driver.

"Their response to her leaving Esaiah on the bus was giving her three days paid suspension," said the family's attorney, Tim Hatton.

"I don't think someone like that should be allowed to be around children," said Julie Vickers.

The Sumner County Board spokesman said the board has no comment because of the pending suit. He did confirm that Chandler is still working as a Sumner County bus driver.

The lawsuit also alleges that the driver slapped Esaiah's older brother and another child on the back of the head a month later. The family said this occurred because the family filed a complaint against the driver over Esaiah being left on the bus.