system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What's the difference between murder and culpable homicide?

I've been asked about this on Twitter, by someone who is struggling to understand how Oscar Prestorious can be not guilty of murder, when he knowingly fired four shots into a bathroom where he believed an intruder to be.  She says, even if he thought it was an intruder, the mere fact that he shot with the intention to kill another human being makes it murder.  Can somebody please explain the legal differences and why those differences are an important aspect of a fair justice system?

I'm an anthropologist, not a lawyer, so even though I (mostly) understand the differences, I can't break it down and explain it in a way that would be useful at all.
gpt
Pistorius was charged with premeditated murder, which implies that he had planned on killing Steenkamp at some time in the future, meaning if he hadn't killed her that night, he would have killed her some other time. In the eyes of the judge, the prosecutors didn't prove that he had planned out her murder, so she ruled in Pistorius' favor. 

He was found guilty of culpable homicide, which implies he may not have meant to kill her. Pistorius claims he thought she was a home invader. The judge found him guilty of culpable homicide because he was negligent: he didn't call the police, he didn't give whoever he thought was inside the bathroom any opportunity to escape, he simply fired through the door, which killed her.

EDIT: Spelling.