I think they appear at random times of the day. Only a certain amount of people can be on the map at once, some pyscho survivors may have replaced the snipers. If you go around and kill all the survivors then they should respawn. But I'm slightly unsure as I didn't play sandbox mode for long.
Hey there, just wanted to say thanks for the great DR2:OTR guide. Do you know how the psycho's work in Sandbox mode? Do they only appear at certain times? All the snipers were out for a while, but they seem to have disappeared now. Also, once you kill one in sandbox mode, do they respawn later or are they gone for good?
I actually had about half already when the list came out. There was also a lot of easy trophies, so those games I rented from gamefly. Some of the others I bought used and sold when I was done. Really only a couple games I had to buy new. Trust me, I'm not rich either. Wish I was...