Here is a link to the report of the checkpoint killing by William Branigin of the Washington post."You just killed a family because you didn't fire a warning shot".

And this is the crucial bit for me: "To try to prevent a recurrence, Capt Johnson ordered that signs be posted in Arabic to warn people to stop."

Confirming that such signs had not been placed previously. What kind of preparation has this army made for the very predictable situation they find themselves in? I think it is nonsense to suggest that putting them out at the time of setting up a road block would have meant putting soldiers at unreasonable risk of attack.

Even from a military point of view, in a situation like this, avoiding deaths like this has to be an absolute highest priority.