As if Lucien wasn't already revolted enough by the fact that Lyssandre and the Remilly family were responsible for the spread of the virus as well as Anastasia's cruel death, he has come to learn more harrowing things about them for the next following days.
Ever since he found out the truth about the origin of the apocalypse, he had locked himself up in his room. He simply didn't know what to do at that point. Everything he learned - it took days to completely sink in.
When they did, Lucien still found himself indecisive, lost and grieving for Anastasia.
Like the coward that he's always been, he wanted to deny reality a number of times. But whenever he tried to, he felt guilty and awful. After all, his friend had sacrificed her life for the truth while he, on the other hand, kept cowering and hiding away from it.
Indeed, he's one big coward.