If he knew, he was obeying the IDF Chief Rabbi's injunction, reported here in Haaretz, 'Show no mercy, they are worthy of extermination.' or words of similar import. He called the Gazans the name of a people that the BCE Israelites failed to exterminate wholly in ancient times. If he knew, the orders were deliberate.
AG examines probes deal by new police chief Hirsch's security firm (Haaretz)
from the article: IDF probes top officers on Gaza war strike that killed 21 family members