CHICAGO (CBS) — Just two days after a town hall meeting to discuss racist graffiti found at Oak Park and River Forest High School in recent days, someone “air-dropped” an image of a swastika to students’ cell phones during a school assembly.

School officials said students were gathered in the auditorium for a “Tradition of Excellence” assembly Friday morning, when someone “air-dropped” the image of a swastika to students’ phones. AirDrop is a feature on Apple mobile devices that allows users to share files with other Apple users.

The school launched an investigation, and Friday afternoon announced they had “brought this particular matter to closure.” School officials did not elaborate, citing privacy laws, but a letter to students, staff, and parents suggested disciplinary action had been taken.

“In this and all other investigations, we cannot identify persons responsible, nor can we share any disciplinary consequences that result. We understand that this response is frustrating for many of you. But we have an obligation to abide by the law,” OPRF spokeswoman Karin Sullivan stated in an email.

The incident comes two days after a town hall meeting to discuss two recent incidents of racist graffiti at the school.

Racist rants including “all n—–s need to die,” the words “white power,” “death to blacks and Muslims,” and “gas the Jews” were found at the school Monday night. A swastika was also part of the graffiti.

According to published reports, an African American teacher was targeted last week with a racist message including the phrases “F*** dancing n*****” and “white power,” along with two swastikas.

School officials said extra police presence has been deployed on campus.

“We are fully invested in protecting the physical and emotional safety of our students and staff, and we are using every resource at our disposal to protect them,” Sullivan stated.

Oak Park River Forest High School was the subject of a documentary shot three years ago. The film, “America to Me,” reveals two different worlds for white and black students at the school.

“We have worked diligently to address that and I think that if you talk to any of our student leaders, they will tell you that they see things changing,” School District 200 Superintendent Joylnn Pruitt-Adams said at the time.