A masked man invaded a barbecue at a Chicago-area synagogue, shouting anti-Semitic slogans, visitors to the event said.

The incident occurred Sunday at the Anshei Emet synagogue in Chicago, which was hosting a kosher food festival.

Witnesses said that the man entered the area where the event was being held and starting cursing and yelling, saying that “all Jews must be exterminated,” and similar comments. He also waved a posted with swastika on it.

Several off-duty police officers were on hand and tried to apprehend him, but were unable to. Police said they would open an investigation. If caught, the culprit could face hate crime charges.

Chicago has long been a center of neo-Nazi activity.

The most well-known event targeting Jews in the area was a 1977 march by the National Socialist Party of America in the city.

City officials attempted to deny the group a license to march, and the group, aided by the ACLU, appealed to the US Supreme Court, which authorized the march.