As soon as he saw him, and heard his voice, his eyes narrowed and he felt something within him break again, just as it had last night. After the talk with Remus, he couldn't handle seeing Sirius's face. The other boy's awful state didn't register in his mind as he strained against Lily. James had enough sense not to try to launch out and risk hurting her arm, but he started to shake with anger and gritted his teeth to try and clamp down the outpouring.
"Morning...? MORNING?" There it went. He pried Lily's arm off of his shoulder and slowly rose from the sofa, letting himself breathe before he went off. He really was trying to remain calm.
"I think we know what happened," he snapped at Lily, not intending to get so arsey with her but being unable to control his anger. "You had a marvellous bloody time, did you?" Throughout the entire cold speech, he'd inched closer to Sirius, fire in his eyes. And when he got close enough to toss a hex, he was undone.
"Too engrossed in that SODDING GIT to bother coming back earlier, WEREN'T YOU? LEAVING REMUS LIKE THAT?!" His voice rose to a shout as he felt his heart racing. The adrenaline was making him see double even with his glasses. If he could swing a punch, if he were closer, he'd nail Sirius to the floor with no remorse.