1. Old age (my preferable scenario)
2. Cancer (have it on my mother's side of the family and both her parents died in their 40s from it, sister was diagnosed with it when she was a toddler)
3. My back (Have metalwork in it from surgery. Any major fall wouldn't be so funny if the metal gets loose from my spine and messes with my insides.)
4. Random apocalyptic scenario (could happen depending on how human society messes itself up or if we get some random space phenomena in contact with our planet.)
The apes are kinda angry and are thinking they want a planet all to themselves.