It says nothing about chasing one down, or shooting them after the attack has ceased. I think you would be in pretty hot water if you shot them while fleeing after the attack was stopped and they had submitted for a period of time.
PC §9.32. DEADLY FORCE IN DEFENSE OF PERSON. (a) A person is justified in using deadly force against another:
(1) if the actor would be justified in using force against the other under Section 9.31; and
(2) when and to the degree the actor reasonably believes the deadly force is immediately necessary:
(A) to protect the actor against the other's use or attempted use of unlawful deadly force; or
(B) to prevent the other's imminent commission of aggravated kidnapping, murder, sexual assault, aggravated sexual assault, robbery, or aggravated robbery.