Only one pair was still battling, apparently unaware of the...

Only one pair was still battling, apparently unaware of the new arrival. Harry saw Sirius duck Bellatrix's jet of red light: he was laughing at her. 'Come on, you can do better than that!' he yelled, his voice echoing around the cavernous room. The second jet of light hit him squarely in the chest. The laughter had not quite died from his face, but his eyes widened in shock.