1) What was sucking all the power suddenly?
could be battery like i posted before
2) Is this related to somekind of computer chip screwing up?
i dont think it could be but if the chip fried(highly doughtfull) it might not start
3) I notice the cooling fan was started up by itself sometime after I shutdown the engine. Is this normal and that's why it lost all the power?
Cooling fan starting up after the engine is pretty normal for most cars with electric fans. couldnt have caused to power loss
4) Is this something i can check and fix it by myself?"
if its the battery you could repace your battery with a smaller one and make sure it wont move. other than that i really have no clue
sorry if it doesent help you