A birds about to die!?

there's this bird in my backyard, and this morning my mom took some food and water out to it because it seemed like it couldn't fly. Well 2 mintues after she gave it food and water, it flew over the fence and into my neighbors yard and it got run over by a lawn mower, but it was found on my driveway. Its neck seems to be broken, but we put it in a shady place... one hour later is is still breathing but its not moving. Its not a house pet its a wild little bird. What should i do? Will it die soon?