Sorry, just to clarify my 'several sorts of murder...' imprecision - bold bits from Godot's link
MURDER – DOLUS DIRECTUS
Dolus Directus (direct intent), is where the accused meant to perpetrate the prohibited conduct, or to bring about the criminal consequence and where the consequences of an action were both foreseen and desired by the perpetrator. You want to kill someone, so you shoot him. In this case the perpetrator had a specific victim in mind and then went about killing him
In Pistorius' case he would have to know for sure it was Reeva there.
MURDER – DOLUS EVENTUALIS
Dolus eventualis exists where the accused does not mean to actually cause the unlawful consequence which follows from his conduct, but foresees or should foresee the possibility of the consequences ensuing, and nonetheless proceeds with his conduct.
It’s important to understand that in this crime, the identity of victim and existence of motive are not in question, what is in question is whether the conduct itself and the way it was done suffices as in intent to kill.
Until just now, I thought this might be relevant if he killed Reeva thinking she was an intruder, but I see now I was wrong.
CULPABLE HOMICIDE
Culpable homicide has been defined simply as the unlawful negligent killing of a human being. The essential difference with this crime from those mentioned above lies in the fact that the fault in this crime stems from negligence (culpa) and not intent.
I cannot see how he is not guilty of Culpable Homicide given that he did not effectively check whether Reeva was in the bedroom. He did not get any verbal confirmation before discharging his weapon.