The United Nations assembled a fact-finding panel to investigate an attack that killed one staff member and injured another in Rafah, in southern Gaza.

A vehicle branded with UN insignia was targeted on Monday, prompting swift condemnation from international leaders.

Initial assessments suggest the fatal shot was fired from a tank in the neighborhood, striking the back of the UN vehicle, according to deputy UN spokesman Farhan Haq. Discussions are underway with Israeli authorities to determine the circumstances of the attack and the nature of the explosion.

Casualties: The deceased UN staffer was from India. His death marked the first time an international UN worker was killed during Israel’s military campaign in Gaza. The injured colleague, from Jordan, is hospitalized. Both were employed by the UN Department for Safety and Security.

With 71 international staff members stationed in Gaza, the attack underscores the dangers faced by humanitarian workers in war zones. At least 254 UN aid workers have been killed since October, according to the agency.