I don't know anything about how things work in situations like this, but logic would lead me to think a convoy of aid workers wouldn't be returning fire so shooting at them with all the shots coming from the IDF side might indicate some sort of mistake quite early in the encounter. The fact they carried on shooting for 5 minutes is either a signal that they knew and just didn't care, or that they're some of the worst trained soldiers imaginable.
5 minutes is a really short period of time, i can easily believe that a convoy of combatants might not return fire in that time period, especially if taken by surprise at night and the people shooting are under cover and far away so its not immediately clear where to even return fire to.
