Disaster in my Pond.

I am in deep grief over my pet fish. I just buried my beautiful orange & white Koi whom I've had for about twelve years. He was as big as one of my cats. He didn't have to die.
I also lost about fifteen other beauties.
I am totally devastated as it's all my fault. I left a lever turned up instead of turning it back horizontal when I realized my backwash pump was broken yesterday. As a result all the water pumped out over night. There was barely inches of water in one end. During the night some critter got in the almost empty pond and ate several. There were dead fish lying on upper shelf and I buried them in my garden. This is him swimming with his brother and many of the other recently departed fish.