In Sirius's panic he missed Amelia's eye roll. Had it seen it, there may have been a couple more bloody faces. Who was she to judge their relationship? James was literally the only person in the world Sirius would die for. Sure he loved Andromeda, Regulus, Remus, and Peter, but James was different. Not only was James Sirius's brother, but he was his best friend, and identical in every way except looks. And the fact that James was into one girl, where as Sirius liked every girl except Lily. Regardless of their minor differences, sickness and dread cursed through Sirius when he saw the blood.
When James spoke with ease, Sirius relaxed a bit. Certainly if he was dying he wouldn't be able to speak, right? Concern was written all over Sirius's eyes, an emotion that rarely found itself there. Taking a step closer, Sirius kept a bit of distance. He'd heard the 'stand back, give her some space' chant time and time again. Besides, if Amelia was taking care of James that wasn't a bad thing. She was a good looking bird, and she played Quidditch. But Lily...
"Oi! P--James what in bloody hell happened to you?" Sirius was still working on not calling James 'Prongs' at all times. Even at a time where Sirius was freaking out, he couldn't stifle the giggle. "Sorry, I mean... you are bloody." Yeah, he definitely wasn't the mature one.