What Causes Brain Aneurysm?

Hello, my name is Madison and I ve been acknowledging one of my dad s close friends death. He was in Africa on a business trip, and suffered a terrible death, a brain aneurysm. However, I have been greatly curious about his death because he had no symptoms of a brain aneurysm, and died suddenly. Coming to conclusions, and thinking about other possible causes of his death, I have finally realized that he could have possibly been poisoned. I know that s probably not the case, but I don t think that it was a brain aneurysm like the doctors want everyone to believe. So I would very much appreciate your help on this. Also, what s your opinion? Coincidental brain aneurysm? Or murder? Thanks in advance.