Tree shedding leaves suddenly?

Question

I live in Malaysia and we have the sun all year round. I have this big tree outside my house and it grew beautifully. Yesterday it was still in good condition but today it most of the leaves drooped downwards and many fell off. There was rain lately so I don't suppose it is because of the lack of water. My mom suspects that someone else was envious of our garden and gave poison to the tree >.>

Are there any other reasons for this phenomenon?

Answer 1

A sharp poison might have affected the tree or check the insect attack if any

Answer 2

My observations is that it is actually a natural phenomena or if not some animals or insects or even people have injected some substances like stings or poisons.

Answer 3

Another possibility is that it has been affected by a root fungus (pathogen) like phytophthora ... this is not a fungus that will produce toadstool-like growths around the base of the tree (like Armillaria).