That all depends on the circumstances. If you get in a fight, punch the Guy and he falls over, hits his noin and dies, then technically it is manslaughter, as you intended to harm, but not kill.
Murder need not be premeditated as it could be a spur of the oment decision, such as the killing of this Police Officer. I am sure they did not intend to kill anyone, but they did, and that is murder. You cannot shoot someone and later claim you only meant to hurt them a little bit, unless you can show your skill with the weapon is such that had you intended death then the person would be dead...
It is largely immaterial as the CPS and Police seem to treat all unatural deaths as murder.