Israeli forces in Gaza killed Hamas leader Yahya Sinwar, a chief architect of last year’s attack on Israel that sparked the war, the military said Thursday. Troops appeared to have run across him unknowingly in a battle,

Sinwar, the leader of the Palestinian Islamist Hamas movement in the Gaza Strip. Foreign Minister Israel Katz confirmed the death of the much-sought-after Hamas leader, after earlier reports of his demise.

In northern Gaza, an Israeli airstrike on a school sheltering displaced Palestinians killed at least 15 people, including five children, according to Gaza’s Health Ministry.