Why Max died...

Question
Dear Sandra,
I was wondering if you might be able to help me figure out why my pet rat passed away. I'm sure it can be any number of reasons, and without a necropsy would be impossible to confirm, but i thought you might have an idea.
I've only had Max for 5 months, but he was almost 2 years old. Unfortunately, i was gone on vacation for 10 days when he died, so i have no details of the few days prior. We had 2 different friends come by the house to check on/play with/feed them. They noticed nothing abnormal, Max came out of his house and ate his treats with the other rats. Of course not being rat owners themselves, they would'nt notice a slight change or symptom.
The one who found Max dead a few days before we came home says Max was laying on his side outside his little house with his eyes closed. I wonder if the closed eyes means anything, because it has only happened with one other of my many rats who have passed away over the years (either naturally or by euthanasia) that died in her cage with her eyes closed. Could Max' eyes being closed mean anything?
Our friend put him in a box in the freezer. I looked at him when i got home and saw that a reddish-brown liquid was around his rear. I don't think it was pee because there was a little drop of pee on his penis and it was clear. So i guess it must've come out his bowels. When i cleaned the cage, the little house had some of that reddish-brown liquid on the bedding. It wasn't thick like blood, nor brown like diarrhea, but like a watered-down blood. It didn't smell like poop either, but it did smell bad, like death.
The only other clues i have are: I remember thinking his breathing looked a little labored right before i left, no noise, but his sides went in and out more than usual (I feel so bad i wasn't there to start him on meds if necessary). Also, he had slowly but steadily lost weight since i got him, from 505g on Aug 27/10 to 346g on Jan 10/11. (I thought at first he might just be loosing a little weight because he was kind of fat when i got him, or maybe he didn't care for the food i give them, though he did eat it. So near the end i was offering him a bigger variety.)
I wish so much i had been around for him. I feel horribly guilty. I know it was just bad timing, but i really wish i had been here, to see any signs and give him antibiotics and at least be here if he still did pass away. I just really hope he didn't suffer. But i would really like to know what he died from.
Sandra, do you have any idea from my very few clues? The reddish-brown liquid? The closed eyes?
Thank you so much,
Joleen

Answer
I am so sorry for your loss. DO NOT beat yourself up over this....sadly these things happen, often when we dont even expect them to happen, which only makes us feel worse!  The closed eyes mean nothing, really....some rats die with them open, other times they close.  It could have been anything, from infection to heart trouble.  I wish I could help more.  The weight loss and heavier breathing could indeed be indicative of heart disease, but it really would not be fair to say for certain without knowing his history and status of his health before he passed.

Just know that you did the best you could for him and gave him a happy life. Thats all that matters.