(CBS) – The FBI is stepping in to help Northwestern University police after at least four incidents of racist and anti-Semitic graffiti on the Evanston campus.

The first two happened in April at the university’s library, one in a conference room and the other in an elevator.

This month, there were two more incidents. The first was at the construction site of the new Kellogg School of Management. The second was at Ryan Field, where a swastika was drawn on a dirty window.

Many on Northwestern’s campus are unhappy about the incidents.

“It’s disappointing. It’s unlike Evanston, and it’s unlike the campus,” university employee Hillary Bean says.