In the after-credits scene of episode 2 of 91 Days, Nero questions Avilio about the circumstances of Vanno's death. Crunchyroll translates the dialogue as follows:
AVILIO: He stole Vanno's gun. I shot Serpente, but it was too late.
BARBERO: Your hands weren't tied?
AVILIO: Serpente said he'd let me pray. Then he tied up Vanno...
Is that actually his alibi? It doesn't make a whole lot of sense that Serpente would have to steal Vanno's gun if Avilio were already tied up. And why would Serpente let Avilio pray and then tie up Vanno? This doesn't make a whole lot of sense.