It was no longer deadly force when the person was already dead.
Problems with that:
1) he probably would not have to worry about what the grand jury was going to do if that last round had stayed in the pistol;
2) he’ll need to convince the jury that the guy was already dead (yeah, we all know that the state has the burden of proof, but I’ve seen my fair share of juries, and they are going to need to be convinced);
3) Mutilating a corpse is still a felony in Texas, and if Kim Ogg can get the grand jury to indict, you can bet she’ll have that as a lesser included charge.