This is going to be an interesting case. On one hand, it seems quite obvious that he used excessive force, at a time when he was no longer in danger. On the other hand, OK seems to have some very simplistic requirements on justifiable homicide:
http://www.oscn.net/applications/oscn/deliverdocument.asp?citeid=69324&date=
"Homicide is also justifiable when committed by any person in either of the following cases:
1. When resisting any attempt to murder such person, or to commit any felony upon him, or upon or in any dwelling house in which such person is; or,
2. When committed in the lawful defense of such person, or of his or her husband, wife, parent, child, master, mistress, or servant, when there is a reasonable ground to apprehend a design to commit a felony, or to do some great personal injury, and imminent danger of such design being accomplished; or,
3. When necessarily committed in attempting, by lawful ways and means, to apprehend any person for any felony committed; or in lawfully suppressing any riot; or in lawfully keeping and preserving the peace."
Was the robbery in this case a felony? I'm interested in #3 myself...murder is justified if it occurs while attempting to apprehend a felony suspect. Would this *only* apply to police? Can a citizen "apprehend" someone?