There's a pretty good chance this was an own goal.
Posting this before it's clear what caused this is borderline misinformation.
EDIT: this compounds the existing lack of medical supplies and equipment, already stretched extra thin after Hamas stole truckloads of fuel and medical supplies from the UN earlier this week.
Bombing a hospital is half a step behind carpet bombing the whole place. Did not expect it to escalate like this, so I second the motion to get verification
So how did this independent investigation should work exactly, when all the border crossings are closed?
Oh wait Palestinians also don't have access to water, fuel or electricity, they cannot escape to a neighbouring country, they are told to go south, and then bombed even there. But of course none of this is considered a war crime because Israel has the right to defend themselves and apparently the right to designate what amounts to a war crime too.
Israel claims an Islamic Jihad rocket misfired and hit a hidden ammo dump in or near the hospital.
Update:
IDF: An analysis of IDF operational systems indicates that a barrage of rockets was fired by terrorists in Gaza, passing in close proximity to the Al Ahli hospital in Gaza at the time it was hit.
Intelligence from multiple sources we have in our hands indicates that Islamic Jihad is responsible for the failed rocket launch which hit the hospital in Gaza.