He deserves this. He knows he does, the ire and pure fury thrown his way. He's let this happen to Sirius, let him be hurt. Let Bellatrix hurt him, made things worse by being unable to keep up the act. Still, Remus' reaction makes his heart drop into his stomach and his eyes widen - he takes an instinctive step back at the look in Remus' eyes, unfamiliar and terrifying. He's never been frightened of him before this moment, but now he feels like he's looking at a stranger. A stranger that wants to kill him.

(A cruel part of his mind whispers you should let him but he holds the guilt of killing on his conscience. Remus is a better person than he is and he wouldn't wish that guilt on him for anything.)

"I—" Remus has his wand out, could easily strike out but doesn't. Regulus knows better than to let it blossom into hope. No, he knows the impracticality of close-quarters. He's just waiting. Somehow, that hurts the most. "I'm sorry," he croaks out, "I tried to stop her but she wouldn't, I did everything I could but she kept going, she wouldn't listen, it was all I could do to keep her from killing him—" he has both hands raised slightly as he speaks, disarming and empty, flattened out protectively.

"Remus, please. I came to see him, to apologize for not being able to help him." There's something like a sob thick in his throat. "Please."