The boy died from dysentery not from being starved in prison as you imply. He was in there for throwing stones and a Molotov cocktail.
The conditions in the prison need to be investigated as they sound inhumane. They are being investigated though apparently the prison meets the minimum health standards required under Israel law (sounds like these need to be raised according to the reports of malnutrition & dysentery).
Oh and the difference between Israel and Hamas? Hamas is a terrorist organisation.