So very sorry to read this, you will have lots of support on here as sadly at the moment a lot are being lost.
They leave such a big hole my thoughts are with you.
I'm so so sorry for your loss. I know exactly what you are feeling as we lost our beautiful mare today if you need a shoulder to cry on then cry on mine and we can cry together.
So sorry to read of your loss, and feel for anyone who has recently lost a beloved companion.
We lost a horse 18months ago to the same thing, it happened out of the blue all in the course of a day with vets visiting every few hours and in the end there was nothing that could be done.