Trigger warning: mental health emergency

My husband just told me today he wants to hurt himself-he has dark thoughts that hunts him down. He said he loves me and our family that it has nothing to do with us. I offer for him to see someone to help and he said no. He left the house tonight saying he needed some time for himself. Saying he would come back tomorrow. I am at lost. We have a 3 month old baby and a 5 year old. I dont know what to do to help him. My heart breaks and hurts for him.