A school bus aide in Fairfax County has been charged with assaulting a 12-year-old autistic student, law enforcement authorities said Wednesday.

Hyung Lee, 57, of Fairfax was charged with two counts of assault and battery in connection with two incidents in October, according to a news release from the Fairfax County Police Department. Lee, who was suspended without pay, turned himself in to police Tuesday.

The boy’s mother discovered bruises on her son’s arms and reported the injury to school officials, said police spokeswoman Reem Awad.

A supervisor reviewed school bus surveillance footage that showed two encounters between the boy and Lee — one on Oct. 10 and the second nine days later, according to police. The mother then filed a police report, Awad said.

A school district spokesman declined to disclose the school the student attends, citing student privacy. The identity of the child was not disclosed; authorities generally do not reveal the names of young victims.

Lee is the third Fairfax schools employee arrested this week for allegedly harming a child who has autism.

An aide, Edmund Bailey, 35, and a school bus driver, James Duffy III, 62, both of Lorton, were charged with one count each of assault and battery, police said. Bailey and Duffy are accused of assaulting an 11-year-old boy who is autistic twice in one week.

Police said those incidents and Lee’s accused assault are not related.

John Torre, a spokesman for the school district, said in an email that drivers and attendants who help transport special education students are being retrained in proper restraint and intervention.

The school district’s transportation office “will continue to closely monitor the special education bus routes to ensure the safety and well-being of all students and staff,” Torre said.

“When parents put their children on a school bus, it is with the understanding that they will arrive at their destination safely and on time,” Torre said. “Regrettably, the charges filed in these separate cases fall short of those expectations and are breaches of the valued trust of our parents.”