There are a number of reasons why someone can die from homicide in the medical sense, but not the legal sense. For instance, self-defense.
Most places have some variation on these types of homicide:
- Aggravated homicide, where the murder was planned
- 2nd degree homicide, where it wasn't planned but could reasonably be foreseen (e.g. savagely beating someone with a bat)
- Voluntary manslaughter/negligent homicide, such as knowingly driving a car with malfunctioning brakes
- Involuntary manslaughter, such as losing control of your car because of ice.
There's also situations where it isn't a crime at all, but would still be medically homicide. I mentioned self-defense, but someone could get shot by a hunter because they were in the woods without an orange vest. There's also certain cases where it's legal for police to shoot someone, due to an active threat.
All of these would be medically homicide, but only some would be called murder.

Why would they start with the harder one? Samsung is much better funded, and therefore will be a much more difficult case.
And no, it does not matter that Samsung did it first.