Cat Dies Suddenly; What Happened?

Hi everyone. I am hoping that somebody may be able to help determine what could have caused my cat to suddenly die.
It started five days ago in the early afternoon, my cat Lodoaf, who was a three year old, medium hair, orange tabby, began to start falling over to one side (his right side I believe) and meowing and crying.
Lodoaf was a big baby and was very vocal anyways but on this day it was "different" than usual. He began crying, meowing, in a way that was unlikely him. When I responded to him because of this crying I discovered that he was falling over to one side. I petted and comforted him as I stood him back up; I kind of held him there, balancing him and holding him so he was standing upright.
He went outside and laid in the sun for awhile and I again petted and comforted him (he even purred for me when I did). I was watching him closely and he would walk very slowly, almost cautiously, taking five or ten steps before he would stop and then slowly lay down, it reminded me of someone being dizzy.
He wouldn't eat or drink anything even though he wanted to. He stood over the water dish for the longest time just starting at it with his face almost touching the water, but he never did drink.
He feel asleep and I kept checking on him, he was gone when I went on a check up with him and I found him underneath a fifth wheel trailer, he was meowing again but wouldn't come out.
The next morning when I went to go check on him I found him dead. He was no longer underneath the trailer but instead about half a foot, (maybe a little bit less), next to it now.
His eyes were closed and he didn't have the "open mouth" were he looked like he was screaming, as every cat that I have ever seen dead has had.
I don't know what happened and I have four other cats that appear to be fine. I also am scared to death that whatever killed Lodoaf may also do the same to my other babies.
I am baffled as to what happened and to settle my anxiety as well as my mind I would just like to be able to answer the question of "what happened to Lodoaf". If you know ANYTHING that may help answer this question please tell.
Thank you so much everyone!!

Oh, I am so very sorry for your loss kelie...my prayers and thoughts are with you during this difficult time...

in my experience, it sounds like it may have been some kind of poisoning. Do all of your babies go outside? You may want to try to keep them in as much as possible just to be safe. My grandma had a cat that did the exact same things you are saying, and he died in front of her hours later after he began acting that way. He also spent a good deal of time in front of the water bowl, but wouldn't drink much. He would just sit there and stare at it. She still swears it was some kind of poison that he got a hold of.

Is there any chance at all he could have gotten a hold to any type of chemical/poison? 

Hi. Thank you so much for responding. Lodoaf was outside all of the time and yes it is very possible that he may have gotten into or come into contact with something that was poisonous and/or toxic to him.
I am going to do a thorough investigation of my property and see if I come across anything.
I am not sure exactly what I should look for. Could you tell me of some of the things that I should keep my eye open for?
What are somethings that are poisonous to a cat and would create the specific type of symptoms that Lodoaf had?
Rat poisoning?
What about multiple wasps or hornets attacking?
Any ideas, thoughts, suggestions, or comments are welcomed. Thank you.

kelie said:

Hi. Thank you so much for responding. Lodoaf was outside all of the time and yes it is very possible that he may have gotten into or come into contact with something that was poisonous and/or toxic to him.
I am going to do a thorough investigation of my property and see if I come across anything.
I am not sure exactly what I should look for. Could you tell me of some of the things that I should keep my eye open for?
What are somethings that are poisonous to a cat and would create the specific type of symptoms that Lodoaf had?
Rat poisoning?
What about multiple wasps or hornets attacking?
Any ideas, thoughts, suggestions, or comments are welcomed. Thank you.

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It could have been a blood clot, or related to cardiomyopathy - a heart condition that can strike without warning.  This was a medical emergency and a vet would have been more qualified to help diagnose and treat your cat.