Cat became ill and died suddenly

My cat came into the house last night after being outside for several hours. He looked confused and was not breathing right. My first thought was that he had eaten a mouse as he has many times before and that he needed to go outside to throw it up, like he has done many times before. So I put him outside, he was reluctant to go but he walked off. I hoped he would come back feeling better but deep inside I feared something might be wrong. He came back an hour and a half of so later and my son let him in the house and he was worse. He was meowing a distressful meow like there was something really wrong. He was having a hard time breathing and he kept opening his mouth as he breathed and kept holding it open. I knew this was a bad sign. He kept trying to sit down and relax and rub against my husband and I, just like he normally did but he could not get comfortable and kept getting up. I called the emergency vet, then he lied down with his mouth open, still meowing loudly and breathing with his mouth wide open. My son noticed his tongue had turned blue--when I told the Vet he said that I could bring the cat in but he would have to be euthanized because he probably couldn't do anything. He died within about four minutes with his mouth open and fluid came out. I wish I knew what caused his death. He did had a heart murmor. I don't know if he could have eaten a mouse that was poisoned or had heart failure. He was only two and a half years old. Do you have as to why he died. Any ideas would bring comfort as my family and I are very distraught over this.

Answer from KAte
Hi
i am so sorry for your loss and in a cat so young too. It could have been caused my a heart condition as I have heard of young cats suffering from conditions like this and suddenly passing away like this.

or course it is also possible that he ate something bad or even got a bone stuck in his throat but without an examination from the vets afterwards it is impossible to say as i am sure you will understand.

i know you are looking for answers right now, i know i have been in the same position too. this will pass, as will any guilt you may be feeling ( this feeling always comes too, i know).

As the weeks pass your grief will be replaced with all the good memories of your cat and if you are like me will feel the need to give another cat a good home.

best wishes Kate