Why are you skeptical? Who always breaks the treaties that Israel and Hamas make?
Usually Hamas, especially this time since they killed an Israeli solder on patrol in Israel, after they agreed to a cease-firee, which has now infurieted the top guys in the army because they didn't finish what they needed to, and stayed in Gaza in strategic areas until a formal cease fire treaty was established.
Israel offers 10 years of peace, opening the borders, getting countries to rebuild Gaza, but to Hamas, they can't have this, because the Palestinian people might realize that they like having peace, food and water, some fun and more. They can't control people like that, only by fear.
Obviously, their response was to attack Israel again and kill people.