Really, there's only two ways to figure out if anyone did anything deliberately: the smoking gun and the past history. For example, you can safely say someone has committed murder if either you find this person standing over the corpse with a bloody knife in his hand, or you discover that this person has a history of committing murders that fit the pattern of this one. (This is not a point about legal responsibility, I hasten to add.) We don't really have a smoking gun in this case -- we'd need something like a direct order to the Israeli forces that they attack the UN outpost. And I'd be quite happy to bet that, even if such a thing existed, it's long since been converted into ticker tape.
However, on the other prong, we do have some information. According to the Whiskey Bar, Israel targetted a UN compound back in the 80's, killing over a hundred civilians in the process. And, according to The Australian, the Israelis in this instance were warned repeatedly by the UN that their attacks were getting close enough to the outpost to be dangerous. (I should note that anyone who believes that bombs and missiles are "accurate" has clearly never been near a gun. No weapon involving an explosively-propelled projectile, of any kind (so, guns, missiles, bombs), is ever entirely accurate. The closer you get to a target you don't want to hit, the greater the chances that things will go just wrong enough to hit that very target.) So, given a history of carelessness, plus reports of carelessness in this instance, it seems that either the Israelis deliberately targetted the UN outpost -- or they deliberately didn't refrain from targetting it, which amounts to pretty much the same thing vis-a-vis culpability.
So, in other words, Israel is compounding its war crimes, all in the name of self-defense. (I have to say, I find this sort of thinking tempting -- whenever my boss says something I don't care for, I'll defend myself by beating little puppies with sticks. After all, it's just "self-defense" -- the puppies were in my way. And so were the small children. And do I really need to mention the adorable kittens?)