I have heard a sheriff deputy say once that police cannot shoot someone running from them, unless it is at night, unless they first call out to them once or twice, and then fire a warning shot in the air and then shoot them.
Admittedly, there are departments out there with some pretty screwy policies, but only at night? Warning shot? Never heard those before; in fact, I know of NO department that authorizes warning shots, other than military.
The test of whether or not you can shoot someone running from you comes from SCOTUS's decision in Gardner vs Tennessee in 1985. The details are lengthly and mostly involve the use of deadly force for law enforcement, but the crux of the matter relating to this discussion is that deadly force IS authorized against a fleeing suspect IF
the suspect's continued freedom presents a grave and imminent threat to the lives of others, and no other options for apprehension exist. I'm not sure how this would apply to non-LEO's.