I would bet he has cased out his shooting positions many times to see what could be seen from them and how to easily get into and out of them. If they can narrow down where they think he shot from, they should be able to start asking locals if they've seen anybody coming to those spots with maybe binos or a spotting scope lately or doing anything odd like laying on the ground... I hope they catch this scoundrel.
After all these shootings with almost no clues, we have the Benjamin Tasker incident with all these clues, Brass, Tarot Cards, matted grass, dog hits on explosives. I would be putting a question mark after all of these as possible plants.
I know...I think my frustration is just eeking out through my posts...sorry.