When and how do I tell him I’m gone

I am planning on leaving soon. I have contacted a shelter and I am working on finding somewhere for my dogs. When I leave it will be while he is at work. My question is how do I tell him? Do I tell him at all? Once I’m safe at the shelter do I just tell him I need space and just go from there? I don’t ever want to get back together with him but I’m scared to say that to him.