I don't see any weapons lying around here immediately after the attack. These were Hamas policemen, not the Hamas fighting forces.
It was Israel's way of breaking down the internal security infrastructure of the democratically elected Hamas to make way for a return of Wast Bank's Fatah which was expelled by Hamas earlier and their security compounds taken over.
The debilitating Gaza blockade resulting in the Hamas Katushya rocket launches, which are home made tin shells with motors and do not even carry explosives - killing one Israeli (an Arab-Israeli) and damaging some houses in six months - is the same Bush Sr. doctrine previously used on Iraq to make ordinary citizens rise against Saddam Hussein after the first Gulf War. They didn't succeed. In case of Bush Jr. and the Israelis, it is to punish the Gazans for voting for Hamas and for them to get fed up and accept the secular pro-West Abu Ma'zen and his corrupt PLO in their place. That isn't going to happen either. These things have a way of backfiring.
But USA/Israelis are not really known for learning from previous mistakes. They just repeat them over and over again because for them lives of these strange people are worth nothing.