REVERE (CBS) — A bus driver has been fired and a bus monitor has been put on paid administrative leave after a young special needs student was left alone on a school bus for four hours Tuesday.

The four-year-old boy was checked out by EMTs once he was found and is uninjured. His family told WBZ-TV he is autistic and nonverbal.

READ MORE: Man killed during police shooting at Space Force Station in New Hampshire

According to the Revere Public Schools Superintendent Dianne Kelly, the bus monitor is an employee of Revere Public Schools. The bus driver was hired through an outside contractor, VSP Livery Service.

The bus company has since confirmed the driver was fired and that this has never happened in their 20 years of business.

READ MORE: It sounds like Xander Bogaerts would be open to in-season extension talks with Red Sox

Kelly said the bus driver and monitor went through their morning pickup route together. They didn’t see the boy because he was asleep in a booster seat.

When the driver returned for his afternoon route, he saw the boy and called the Revere Public Schools Transportation Department and then brought him to the high school where the department is located. At that point, 911 was called, said Kelly.

A letter to parents from Kelly read in part, “This morning, we reviewed safety protocols and transport expectations with all of our own transportation department employees and with all school principals. We have also been in touch with the transportation companies outside of the district that drive some of our students to school to make sure they have done similar trainings with their employees.”

MORE NEWS: Boston area gets a glimpse of 'super flower blood moon' lunar eclipse

Police and the Department of Children and Families are now investigating.