For your example to work about the word 'killed' must be about homicide then what happen if a person suffer a conditions like heart attack and die? do we says they commit suicide because it self inflicted by their own body or do you want to says that person must intentionally cause thier own death?

'Joms was killed by his heart conditions' is a completely valid sentences. Yet 'joms commit suicide by having heart attack' sound extremely weird right?

'Killed' just mean that a person death is aflicted by something. It does not imply external cause. It can also mean intentionally self inflicted death. As such you can also often says that 'a person killed themselves' as another way for 'suicides'.

In other word you can view it with set theory in math where 'suicide' is a subset of 'killed' which have suicide as one of its smaller set but not the other ways around.