"They were killed in their uniforms", writes Jonathan Whittall, site manager at the UN agency Ocha. "They drove clearly marked vehicles. Wore their gloves. On their way to save lives. This should never have happened."
He himself was on site where the attack took place, but only a week later, since Israel's military initially did not give permission for "operational reasons".
At the same time, Israel's attack is described as the deadliest of its kind in at least eight years.
The Civil Defense and Red Crescent ambulances came here, one after another was hit, attacked, he says in a video published by international media.
"Deadliest attack"
The bodies were gathered and buried in this mass grave, he continues, pointing to the sand.
The vehicles, ambulances from the UN and Civil Defense, were crushed, dumped, and covered with sand here beside.
Fifteen victims of the attack have been found dead, including eight from the Red Crescent, six from the Palestinian Civil Defense, and one UN employee.
"This devastating event is the deadliest single attack on Red Cross and Red Crescent personnel anywhere in the world since 2017", writes the International Federation of Red Cross and Red Crescent Societies (IFRC) in a statement that condemns the attack and points out that international law requires that humanitarian and medical personnel be protected in war.
Harsh UN criticism
The UN's human rights chief Volker Türk also condemns Israel's actions in unusually sharp language.
"The case raises significant questions about the Israeli army's conduct during and after the incident", he writes on the UN human rights agency's official website.
"An independent, immediate, and thorough investigation of the incident must be conducted, and those responsible for violations of international law must be held accountable" Türk writes on Tuesday.
Israel's military has responded that soldiers opened fire because the vehicles "moved in a suspicious manner" towards Israeli forces. They also name a Hamas man who is said to have been "eliminated" along with "eight other terrorists" at the time.
The description of the Hamas man does not match any of the killed aid workers, and no other bodies have been found at the site, writes the AP news agency.
