A bus driver and attendant who were fired Tuesday after leaving a 4-year-old student with special needs on a bus for hours broke several procedures, said Hosanna Mahaley, the District’s state superintendent.

After the boy was picked up Tuesday, he was left on the bus and was not discovered until the employees returned for an afternoon route, she said.

A driver and attendant are required to check the bus after students are dropped off and again at the bus yard. The employees did not make the checks Tuesday. The attendant is required to sit in the back of the bus. The attendant sat in front with the driver, Mahaley said.

The employees also had disabled a safety alert buzzer that activates when someone is left in the back of the bus.

Mahaley described the incident as gross negligence. “It was a rare and bizarre and unacceptable event,” she said at the mayor’s bi-weekly news conference Wednesday.

The driver had worked for the city for 10 years; the attendant for five, she said.

They both wrote apologies to the boy’s family, she said.

The Office of the Attorney General is investigating, she said.