The rumor is a counter-protestor (pro-Isreal) started pretending to be an antisemitic pro-Palestine person and everyone there shouted him down. Again it's just a rumor that I read. I feel like these days its getting harder and harder to really know anything, but I have a hard time imagining ACTUAL antisemites would take over a college campus protest.
On the other hand I do acknowledge that ACTUAL antisemitism have been huge problem as they appropriate the pro-palestine movement to further antisemitism, as I have seen in wayy too many places online these days (Just to make sure I'm clear- criticizing Israel isn't antisemitism, but saying Jews secretly control the world and every Jew is secretly pro-Israel certainly is).