He was killed by the inhabitants of Far Harbor. This act would cause the confessor at the time, Martin, to be hateful towards the settlement's inhabitants. After some reflection, Martin would blame himself for the loss of his parishioner.
↑The Sole Survivor: "What happened to this missionary?" Tektus: "A foul atrocity.Our good Brother Andrews had decided to brave the Fog and attempt to bring Atom's Light to that ghastly town... and remind the heathens of their trespasses.From what I hear, he'd barely spoken a word before they cut him down in cold blood. For nothing more than his devotion. Beasts." (Tektus' dialogue)