It is a relatively simply matter to distinguish the impact of 155mm howitzer round and a land mine. Indeed, with a distribution of six rounds fired from the same battery it would be easy to plot the geographic coordinates of the target, and the likelihood of an "overshot" impacting on the beach. Kofi Annan has appropriately offered an independent inquiry and this required.
An earlier horrendous shelling incident occured in 1996, during a punitive attack by Israel in South Lebanon, the so-called "Grapes of Wrath" invasion. The content of the report prepared then is instructive.
When Israeli forces shelled the United Nations forces in southern Lebanon in 1996, and killed about 100 civilians who had taken shelter there, the IDF claimed that the base was not its target, but a thorough analysis by a competent team of officers under General Franklin van Kappen established that the base was in fact the target for the shelling. The report did not suggest that the IDF intended to kill civilians, and surely they did not, but that they had probably fired at the base intentially. The report concluded: "While the possibility cannot be ruled out completely, it is unlikely that the shelling of the United Nations compound was the result of gross technical and/or procedural errors."
BBC NEWS | Middle East | Beach deaths 'not Israel's fault'