Help, 4yo grandson killed my finches

He tore their heads off. When I asked him why, he told me, with a flat affect, that he didn't do it. I told him their blood and feathers were on his hands and he looked me straight in the eye and said" they didn't like me so I tore their heads off." I am beside myself with grief and fear for the child. I called his mother, my daughter, and she got him an appointment to see a shrink tomorrow. I am in shock, I just keep seeing their little bodies and his little hands covered in blood and feathers. He has not walked this earth long enough to be evil. His parents just divorced and his other grandmother keeps telling him my daughter is going to leave him and never come back. I am so scared for him and of him, he has a little brother. I feel bad for even thinking this , but I don't think he should be left alone with the baby now. What do I do, I love him. I love both of them. What do I do?