Buffs vs minions damage order

I have a hell knight with Magma Diver, Massacre and Reckless Abandon among others. When I attack a creature who has War as a minion, my creature dies before splashing is triggered. The description of splashing says that the creature would deal damage to adjacent creatures to the target they attack (all of them thanks to Massacre). It looks like this damage will be done at the same time of the attack. War description says that after war’s master is damaged, it would deal damage to the enemy equal to 50% of the damage taken. It looks like the damage will be done after the attack. So, if I understand correctly, splashing should happen before war. Why is war killing my creature but splashing does not kill the other enemy creatures or even gets triggered? Is this a bug or intetional? If it’s the second, could someone explain me the order/priorities in damage calculations of combat, please?