I’m so, so sorry 
My condolences.
That was my thought, but the dog did chew through a leash. Perhaps the dog fainted or such- just that in my experience dogs are so boistorous and want to get out.
In any case the OP feels dreadful. I am so sorry for you.
I too feel your pain. I would be horrified if that happened to me.
I also wanted to say that I just now saw this thread and I created another thread here in MPSIMS that some folks are invariably going to interpret as anti-dog, which it isn’t, so I apologize ahead of time.
Sorry about your loss.
I’ve been thinking about this thread since you posted it, The Fine Print. It’s an awful situation, and I couldn’t feel worse for you. It sounds like you and your family are true animal lovers. But I hope this incident can springboard that into something more. Volunteer work, advocacy, fundraising, awareness, etc. are all things that I think I’d be getting involved in if I were in your situation. I cannot imagine the guilt I’d feel if I caused something to harm my dogs. My deepest sympathies.
Fine Print, I am so sorry. This would be devastating for me, and I’m sure it is for you, too.
I’m so sorry to hear this. I can only imagine how you must feel.
I just went to the other room to give my rat terrier a big hug.
How horrible. I’m sorry.
This is actually one of my greatest fears. We have a lot of animals – 2 dogs, 1 cat, 3 birds, and a hamster at the moment – and I’m constantly checking that the birdroom door is secure, that the hamster’s water bottle has been filled, and so on. But I do not harbor the illusion that I will be perfect.
Let me add my voice to the chorus of condolences. Such a tragic, heart wrenching story, brought tears to my eyes. I can only imagine the pain you must be in, you poor thing.
Just so you know, there is not a person, walking this earth, who has not, at some time, momentarily forgotten that which they are normally ever vigilant about.
He’s a beautiful dog, such a lovely photo, looks a real charmer. Try to stay focused on the joy you brought each other and the love you shared.
(Here’s a little trick to help you over your broken heart. Sitting quietly, with you mind focused, imagine another poor soul, on earth somewhere, right now, who is suffering a similar loss, their dog, their child, their Aunty, their oversight, a single time, their heart shattered. Now manifest some compassion for them, in your heart. Shouldn’t be too hard, you literally can feel their pain. Using the depth and breadth of your pain, and the focus of your mind, send them compassion. Feel the compassion for them, their loss, their pain. If you can remember to do this a few times a day, for a few days, you can speed up your own healing. Your subconscious will make the connection between compassion, deeply felt and focused, for another and self compassion. Because that is what it will take to move forward, compassion for self.)
I will remember you in my prayers (at the Buddhist temple) in the weeks ahead. I wish you peace and good luck.
There, but for the grace of $deity_name, go we.
I’m so sorry. I shouldn’t read posts like this at my desk at work, because they always make me cry. I can’t even begin to imagine how horrible you must feel.
This is so true. We would like to think that we are more careful than someone who drove distracted or forgot something like this, but really, we all have moments of inattention, and we’re usually just saved by the circumstances - no car in the oncoming lane when we swerve, or someone else remembers the dog, or it’s a cool cloudy day. I’m so very sorry that everything aligned against you instead of saving you from a normal human blip this time. Really, try not to beat yourself up too much.
This is going to make me even more extra careful in the future. Who knows, your post may save a dog one day.
Please don’t be too hard on yourself. It was a true accident, and they happen to the best of us. I work in the vet medicine industry and people I know - professionals! - have made similar mistakes. We do the best we can with vigilance, but no one is infallible. You obviously loved that dog, and she had a grand life with your family. Though her ending came too soon and unexpectedly, there’s no way to say she suffered long or that a more “natural” end at a later time would have been more kind. There’s no telling, there’s no point in speculating. Just know she was obviously loved and cared for in the best way, and she had a life with you that many dogs would envy. I’m so sorry for your loss. Please forgive yourself. I’m positive that lovely dog would.
I am so sorry. I can only imagine how sad you feel, but please try to forgive yourself. Mistakes, no matter what the consequences, are mistakes. We all make them.
Yeah, I couldn’t finish reading your post. I knew the jist of it. Stories like this are just so hard to bear. I’m sorry this happened. I know it doesn’t make it any easier to say it could’ve happened to anyone. Poor Maggie.
Thank you all for your kind words.
There have been so many replies that I will just address them in general. It’s true that my OP is probably almost as hard to read as it was to post. Like almost all of you have guessed, it is a (long-shot) attempt to possibly save some other dogs life someday.
With a day to gain some perspective, it seems that Maggie did succumb quicker than most dogs. Her suffering wasn’t what it might have been. Thinking about it, I do believe she didn’t feel betrayed at the end. Dogs always forgive their owners a vet visit, no matter how painful. Since they don’t know their own mortality, she probably went unconscious not doubting we’d eventually get to her.
At least, that’s what I hope. I will never know but I feel a little better.
I will try and do something in Maggie’s memory. One other thing is to make my future eBay auctions donate proceeds to a charity, like the ASPCA or the Humane Society. Other ideas are forming as I look forward rather than backwards.
Something I’ve learned by reading last night: A cracked window won’t help a dog or baby left in a car. Maggie died on a cool spring day so the outside temperature doesn’t really matter. I suppose a winter day might be safe but I wouldn’t want to risk it.
Bella is sad and we have decided to get her a companion likely next week. One thing (of many we are thinking about) is that the two dogs will be sure to get a treat when they return from a walk. This will be one more check against this ever happening again. A good friend suggested putting something valuable in a car so you are sure to return.
Thank you again for your caring.
Some specific replies:
Martin Hyde, you are right. We killed our dog through just a few minutes inattention and we are still asking ourselves why (if there is a reason).
FoieGrasIsEvil, your username alone says you care for animals. I agree with your thread and will likely post in it. EVERY trip in a car has a chance of an accident (another driver if nothing else) and dogs withstand car accidents worse than people (no seatbelts or airbags to protect them. Our dogs didn’t go in a car short of a walk or a trip to the vet. But we certainly are in no position to judge (especially now) someone else. Some dogs do enjoy a trip in the car for its own sake. And some pet owners will never have a problem with their pets in cars (just a few days ago, that WAS us).
elbows, your ‘trick’ is working and I had my doubts. Thank you, I will carry that with me and tell it to others.
When we get a companion for Bella, I hope to upload a picture of them both.
I’m glad that you’re feeling a little better and I’m glad that you’re planning to adopt another dog. While it is tragic that this happened, maybe some good can come of it from rescuing another dog at the local shelter who might otherwise not get a chance.
I believe you have misunderstood FoieGrasIsEvil’s username.
I’m very sorry about your dog. 
She’s so cute in that picture. I can’t even imagine how awful this must feel.
My deepest, deepest sympathies. How sad.