Does anybody know why they do this in movies?

Question

For example, the killer stabs somebody and then throws them out the 2 story window. Or the killer stabs somebody and then chokes them. Why do they need to do something before if that's not the way they're gonna kill them?

Answer 1

depending on the the movie, but my guess is that the killer is so full of rage and or malice that stabbing is not enough.  it's not just about the kill but having power over another person

Answer 2

So that the killer won't have a chance of dying when he actually KILLS the victim? wut.