If a fleeing criminal is sufficiently dangerous, it may be justifiable to use lethal force to stop his escape.
You may want to check your state laws on that one, I know in GA shooting a fleeing felon who may pose a threat to the community only applies to Peace Officers,
When Peace Officers use deadly force the court must apply 16-3-21 and 17-4-20. When a civilian shoots the court only apply OCGA 16-3-21.
"Sheriffs and peace officers who are appointed or employed in conformity with Chapter 8 of Title 35 may use deadly force to apprehend a suspected felon only when the officer reasonably believes that the suspect possesses a deadly weapon or any object, device, or instrument which, when used offensively against a person, is likely to or actually does result in serious bodily injury; when the officer reasonably believes that the suspect poses an immediate threat of physical violence to the officer or others; or when there is probable cause to believe that the suspect has committed a crime involving the infliction or threatened infliction of serious physical harm" OCGA 17-4-20.
The following examples are provided to show when an officer may use deadly force:
1. When the officer reasonably believes it necessary to defend his/her own life or the life of another, or to prevent grave bodily injury to him/her self or another and all available means of defense have failed or would be inadequate or dangerous under the circumstances.
2. When necessary to prevent the commission of forcible felonies;
3. To effect the arrest of a person at the scene of a crime who is attempting to escape, but only if there is a serious threat of immediate danger to the officer or third persons, such as the use of firearms or taking of hostages.
When a civilian shoots the court only apply OCGA 16-3-21, which states;
16-3-21.
(a) A person is justified in threatening or using force against another when and to the extent that he or she reasonably believes that such threat or force is necessary to defend himself or herself or a third person against such other´s imminent use of unlawful force;
however, except as provided in Code Section 16-3-23, a person is justified in using force which is intended or likely to cause death or great bodily harm only if he or she reasonably believes that such force is necessary to prevent death or great bodily injury to himself or herself or a third person or to prevent the commission of a forcible felony.
(b) A person is not justified in using force under the circumstances specified in subsection (a) of this Code section if he:
(1) Initially provokes the use of force against himself with the intent to use such force as an excuse to inflict bodily harm upon the assailant;
(2) Is attempting to commit, committing, or fleeing after the commission or attempted commission of a felony; or
(3) Was the aggressor or was engaged in a combat by agreement unless he withdraws from the encounter and effectively communicates to such other person his intent to do so and the other, notwithstanding, continues or threatens to continue the use of unlawful force.
(c) Any rule, regulation, or policy of any agency of the state or any ordinance, resolution, rule, regulation, or policy of any county, municipality, or other political subdivision of the state which is in conflict with this Code section shall be null, void, and of no force and effect.
(d) In a prosecution for murder or manslaughter, if a defendant raises as a defense a justification provided by subsection (a) of this Code section, the defendant, in order to establish the defendant´s reasonable belief that the use of force or deadly force was immediately necessary, may be permitted to offer:
(1) Relevant evidence that the defendant had been the victim of acts of family violence or child abuse committed by the deceased, as such acts are described in Code Sections 19-13-1 and 19-15-1, respectively; and
(2) Relevant expert testimony regarding the condition of the mind of the defendant at the time of the offense, including those relevant facts and circumstances relating to the family violence or child abuse that are the bases of the expert´s opinion.