Murder = Planned homicide
He didnt plan to kill him. Thus = Rash Act.
First of all I need to say I used to deal with the law before... though not indepth but got very very very basic knowledge of it...
if u look at the law book
Exception 1 When culpable homicide is not murder.
Culpable homicide is not murder if the offender whilst deprived of the power of self-control by grave and sudden provocation, causes the death of the person who gave the provocation, or causes the death of any other person by mistake or accident.By grave and sudden provocation (such as u caught your wife sleeping with another) u kill another, u have committed culpable homicide. But u have not committed murder.
There r 3 level
Murder = always give death penalty
culpable homicide = maximum life time imprisonment
rash act = 2 years jail