Having spent time in Africa, AFG and IRQ, i can see exactly how this happened.
The food trucks pulled up and young healthy men rushed the trucks, grabbing whatever they could, shoving the women and children out of the way. From all accounts, many of these young men were Hamas and began shooting at people in their way. The trucks started to move away because of the craziness and even more rounds were fired.
Some of the rounds went toward the IDF and they returned fire, causing everybody in the crowd to go ballistic.
Was that pun intentional?