To Know Death / To Know About death.

[Carmelita]

I would argue that you are both right. Whilst the technical meaning is the same, the former is indicative of impact, whilst the latter lacks it. A general might know death, a doctor might know death, a coma survivor might know death. A sheltered historian might know about death but not know death, while a young child losing a loved one might know death but not know about death.