Regulus waits until Dumbledore is gone before he speaks again. When he does his voice is shaking and he looks like he's about to cry--"I'm fine," he manages, "I don't need to lay down."

It just goes downhill from there, even though Sirius is standing here in front of him, isn't physically broken anymore. "I'm so sorry," he gasps out on a sob, unable to keep it in anymore even though they're still in the entryway. "I'm sorry for--everything, for not being able to stop her, not being able to help you, I had to leave you, I understand if you hate me--"

He hasn't let go of Sirius' hand though, clutching at it desperately. It's like he hasn't even registered the good emotions in Sirius' voice.