Since when do visits from guards lead to enlightenment?
Thorium, mana doesn't matter, so what do we do? Let him continue to kill our people because he doesn't care? :/ So, who do you suggest we execute? Do you have a better idea?
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Since when do visits from guards lead to enlightenment?

Well, imagine yourself in the nurse's position: you see this, and who would you report it to first? I would probably call the police, or the security guard. A priest would be the last person I'd go to, but that reinforces the fact that he definitely didn't have anything to do with what happened to Laura (the priest).
Ha. Maybe he was protected by both a guard and a priest. And Gil, who is supposedly a guard, adheres to the version with a guard precisely because he is the one who used the Night Blade on Hostor?
So, he's not a doctor, or a guard, or a watchman, or a psychopath, or a policeman. Who is he? A priest...
Yes, that's true... But on the other hand, Pitch Black is definitely not guilty of what happened to Laura. So, he's not a doctor at all, and he's not a guard either, not a watchman, not a psychiatrist, not a police officer. Who is he? A priest... He probably wouldn't have spared a guard... The chief physician, even with all his kindness, could theoretically be involved in Laura's death...
Sky, please reread the Prologue. :/
We read the Prologue. When Laura's parents were already in the hospital after Laura's death, the position of chief physician was vacant. Reila wasn't even here at that time; he couldn't have been involved in the death; it all makes sense. So, along with the title of the night, I'm almost certain about the deaths of Cherletti and Reila.
Why Arandor Cherletti?
He didn't take anything from his victim's pockets – no money, no keys, no box of vials.
He prefers insulin-shock therapy.