Parent sparrow killed

Hello,

A pair of house sparrows nest above my window, right now they have chicks. This afternoon I witnessed one adult bird being plucked by a buzzard on the lawn, since then there has been no parents visiting the nest and the babies are continually calling out for them. 

If the dead bird was one of the parents, is it likely that the other has abandoned the nest? Or just avoiding the area for a while? There’s no way to access or look into the nest as it goes under our roof, but the chicks must be at least a couple of weeks old now. Any insight/advice? Thank you.