It's highly likely. When the unrest is about to end peacefully, the best way to reignite it is to send a few snipers to shoot random people on one or both sides of the conflict. Blood magic is very powerful.
Additionally, a typical protester is not likely to own - or need - a quality long gun with a Leupold scope. He is happy with a throwaway "Saturday night special." Long range fire hints at involvement of someone at least minimally experienced in such a thing. City folks rarely have a chance - or a need - to shoot a long gun at 300-500 yards. Over here 100 yards is the maximum distance at ranges; there is one with 200 yards, but it is rarely open to the public.
Presidentially sanctioned black ops?