An African-American South High School student was “subjected to racial slurs and physically attacked” by an older white man on a public transit bus after school Wednesday, according to a statement released by Denver Public Schools.

“We are outraged and deeply concerned about this apparently racially motivated attack on one of our students,” Superintendent Tom Boasberg said in the statement.

Witnesses said the attacker appeared to single out the student based on race, according to the statement. Bus passengers, including other students, intervened and the attacker left the bus, it says. The student recovered, the statement says, and was able to return to school the next day.

Boasberg said he’d spoken with the Denver police chief and that DPS is working closely with the police and the Regional Transportation District to identify the alleged attacker.

He added that once a suspect is apprehended, the school district would continue to work with the police “to ensure the assailant is prosecuted to the fullest extent of the law.”

Denver Police Department spokesman John White said the investigation is in the early stages, and police still have to identify and interview several witnesses.

“We are not at a point, at this point in time, to confirm there was a racial connection with this assault,” White said.

RTD has committed to providing extra security on the bus route, the district’s statement says. DPS does not provide yellow bus service to its high school students but instead gives public bus passes to students attending their neighborhood school if they live more than 3.5 miles away.

“We wish to emphasize how rare such an incident as this is,” Boasberg said, “and that our students have been safe on hundreds of thousands of RTD rides over many years.”

The statement encourages anyone with information about the incident to contact Denver Police or the district’s anonymous Safe2Tell hotline at 1-877-542-7233.

Families and students who would like to discuss concerns can also call the DPS Family and Community Helpline at 720-423-3054, the statement says.