(JTA) – United Nations Secretary General Ban Ki-Moon condemned the recent killing of four people in a Brussels Jewish museum, as 1,500 people gathered in Brussels to pay respect to the victims.

Also in response to the attack, the Jewish museum in Rome is staying open late into the night Monday, free of charge.

Ban’s spokesman said in a statement that the secretary general “reiterates his strong condemnation of all forms of racism, racial discrimination, xenophobia and related intolerance and trusts that Belgian authorities will do everything possible to bring the perpetrator or perpetrators of this crime to justice swiftly,”

Four people died after a gunman entered the Jewish Museum in Brussels Saturday and opened fire. Video of the shooting has been released but police are still searching for a suspect.

In response to the incident, the Jewish Museum in Rome is opening its doors for free, late into the night.

The museum, located in the complex of Rome’s main synagogue, will open to the public at 8:30 p.m. Monday night and stay open “until late at night,” the Rome Jewish community announced.

“It is a concrete gesture to demonstrate how Judaism wants to remember and at the same time launch a message of courage,” the announcement read.

At this time of year, the museum is usually open from 10 a.m. to 5 p.m.