I do believe that it is dependent upon the laws of the state that they reside in.
For the most part however, yes the police can shoot a felony suspect who is fleeing without getting into trouble for it.
This is just my understanding from reviewing use of force articles and statements from police dept. that have had this come up. Personally I don't feel it is right or that it should be legal, I feel that if there is no imminent threat then deadly force should not be used or even threatened, unfortunately my opinion doesn't hold much sway with the authorities.