Samir Ahmed Awad, 16, of the West Bank village of Budrus, was killed by IDF soldiers. So was Uday Darwish, 21, of Dura and Anwar al-Mamluk, 21, of Gaza.

None of them was a "ticking bomb." Their crime was attempting to cross the separation fence near Ramallah, or the one enclosing the Gaza Strip.

It is not clear yet how Mustafa Abu Jarad, 21, of Beit Lahia in the Gaza Strip, was killed. The IDF denies its soldiers killed him, while the Palestinians say he was shot by soldiers.

Four Palestinians killed in five days. In some of the cases the IDF is looking into the firing circumstances, as the customary IDF spokesman's response goes.

But in one case at least - the incident in which Awad was killed - preliminary evidence shows the soldiers did not follow procedures, failed to use crowd control means, which were not at their disposal, and apparently did not warn the youth.

The basic problem emerging from these cases is not procedural. The problem is in soldiers and commanders' overly-free interpretation regarding the circumstances permitting killing Palestinian civilians who only approach the fence, or even try to cross it, without endangering the lives of Israeli soldiers or civilians.

A few weeks ago soldiers who were attacked with stones decided not to respond with fire. Other soldiers, it appears, opt for the lethal response.

The consecutive incidents in which Palestinians were killed in recent days give the feeling that Palestinian blood may be shed with impunity.

The IDF does not lack advanced means and abundant experience in discerning between a person intent on carrying out an act of terror and one trying his luck in landing - illegally - a day's work in Israel.

When this distinction blurs, the margin for soldiers' interpretation on the ground widens. The rules of engagement become, at best, a retroactive excuse and at worst - a dead letter.

Chief of Staff Benny Gantz must not only probe and bring to justice the guilty parties in the killing, but also take responsibility for putting an immediate end to the killing of innocent civilians.