Masked men have attacked two students who were demonstrating in support of Israel at Chicago’s DePaul University, resulting in minor injuries and raising concern about potential anti-Semitism on the Catholic campus, Reuters reports.

The university said it was working with Chicago police to determine if the assault, which occurred on Wednesday, was a hate crime.

One of the victims was a former member of the Israel Defence Forces who was wearing a sign identifying him as such and inviting conversation, said Josh Weiner, a co-founder of the Chicago Jewish Alliance, who said he knows both victims and had spoken with them since the incident.

University President Robert Manuel said the students received minor injuries and declined medical treatment. “We are outraged that this occurred on our campus,” he said.

Chicago police identified the victims as two men, ages 21 and 27, and said two male offenders struck the 27-year-old about the face and body and pushed the 21-year-old to the ground then fled on foot. Weiner said the students were standing near the student center just off campus property.