2 cygnets murderd

My heart and that from the swans is broken. 2 of the 4 cygnets are death. This is one of them. How can a person do this, they are innocent. Been a lot of the day with them. The male and female were making a nest, the nest was a safe place. The female stout up and felt down again. No strenght. The male in shock. Finaly I could get them to eat something. Lucky the other 2 cygnets eat by themselves today. Again I am crying. I want them to go away where they are now, it is not safe at all. I want them in my backyard, but there is not much food. I would take care of them as always. But how do I explain they need to go somewhere else to be safe.