Can a living fish detect from the (tank) water that another fish just died?

I don't think so. Are you asking this question because some of your fish are picking on a dying/dead fish? This is only because they see that they can get fresh food without a fight. They would pick on a live fish if it didn't put a fight also. Some fish are just like that.

Interesting, but unrelated fact: Humbolt squid change colors rapidly when being caught by humans and other squid then begin to eat it while it is being reeled up by the human.

On the ammonia aspect: Fish usually release the most ammonia when rotting, so ammonia usually only becomes a problem when a fish is severely rotting, or many fish have recently died. Be sure to scoop out any dead fish out of your tank right away. Ammonia is also caused by fish poop.

When a fish dies it starts rotting right away. It would be like one of us being in a room with a stinking corpse.

They don't smell it the same way we would, but they can definitely detect it.

Well I'm not sure about tropical fish, but when I had fish, I had 10 one by one started to die and I took the water to Petco and had them test the water, they said that when fish die they emit aminioa and we can't have fish for about a month until our water gets within normal range... so if you don't change your water or have it tested I suppose another fish would notice (then again they say they only have a 3 second memory) but if I were you I would get the water tested. Don't want that to happen again.

it could,but im not fish expert