Possible Cause of Death for my dog (and how to prevent it from happening again)?

My dog just died this afternoon. For the last two days he refused to eat, just resting / idling for almost the whole day. Yesterday, he vomited several times (yellow in color), so I suspected maybe its because of stomach acid, and he will probably eat sooner or later. This morning I found that there is a pool of blood and several of the yellow vomit. Late in the afternoon I go check on him again he is just idling, but his eyes are empty, pool of saliva below his mouth, and his tongue is out to the right side and his jaw is getting stiffer and biting its own tongue. Soon after he started vomiting a lot of yellow liquid and blood started also comes out of his rectum. He takes a huge inhaling motion through his mouth and several moments later he is gone. I couldn't have brought him to the vet because I live in a remote area, so I was just wondering if I could do anything to prevent this from happening again.

Hello   I'm so sorry to hear about this distressing case.  I'm not sure where abouts in the world you are or what provision of veterinary care is common where you are, but I'm afraid that it sounds as though this dog really did need veterinary attention.  If dogs are not eating / drinking but are vomiting, it is likely that they are losing fluid from their bodies (as in, from the bloodstream).  As well as dehydration, this can lead to electrolyte imbalance (affect the acidity / alkalinity of blood) and can make a dog very poorly extremely quickly.  Fluids into the vein can often help to restore the balance.   I am not clear what caused the vomiting or the possible neurological sign at this stage.  It is likely that your vet would have had to perform an examination or tests in order to find out.  Infectious disease may be one possibility, so speaking to them is still potentially very important. As you have other dogs, they may discuss post-mortem tests.  Wishing you all the best and do please let us know what happens from here.