He was probably trying to find a way home like the rest of us, after the Door spit us all out into different locations. The Null are able to sense our energy signatures- it's likely that he just got too close to a scout.

[He sighs.]

They have been... even during bloody times. They once promised that those who worked with them would not be harmed, and during an attack on us, they attempted to injure and kill everyone except for those who had made the deal.