Beating myself up

I’m really upset about something that happened at work.
I’m a vet with many years experience. I was treating a dog that had been bitten by a snake. I watched him closely and decided he was fine to be left alone, I left him for 1 hour and when I came back he had died.
I’ve cried all afternoon, I’m filled with shame, anger, regret, guilt. I’m just hating myself. I feel like quitting my job. I’m embarrassed to say I actually considered killing myself.
It’s a terrible thing to have happened. The owner trusted me to take care and I said I would and then I made this mistake.
Now I just feel exhausted and kind of hopeless.
I know its appropriate to be upset by this. I don’t want to be ok with it. But I also need to do something more constructive than continually beat myself up. I had 2 other people look at the dog and say that he seemed fine but in hind sight I should have done more.
I’m pretty sure I did the best I could at the time but I still feel like I’m useless.
Thank you for listening. I feel shame sharing my mistake but I need help.