They're aliens. Haha! You're laughing right now, aren't you?

Minato, you looked into its eyes, didn't you? An angel put its image inside of me that way, and as long as I kept my eyes open, the angel kept growing and growing and boom! It came out of my body and killed me.

But once we're dead, the angels can use our voices. Statues don't have voices of their own, you know. We're pretty lucky!