How can I explain to my son his father is clinically depressed?

My son is five years old and I've been facing this issue where his father hasn't been okay. We've been separated for a long time and have tried co-parenting as best we can. Recently he was diagnosed with clinical depression after years of problems and is now getting help and starting medication.The problem is he has also always been incredibly difficult with helping raise our child. My son lives with me and my partner, and his father is able to come whenever he wants tk see him. The idea was he'd come frequently or in the least call to talk with him. He rarely does and on the random days he chooses to see my son it always ends badly.I've become concerned with where his mind is at while my son is spending time with him. After a situation happened where I had to go and pick up my son from his father's house because his father was in such a rage over my son throwing a tantrum my son told me something. Once we were in the car and I had calmed him down he asked if "the police were going to take daddy". That scared the hell out of me because that's never been a topic of conversation. My partner and I have never discussed that because as bad as his father was at being present in my son's life he had never given me reason to see him as a threat to my child.I calmly told my son no, and then asked him why he thought that. My son told me that he wants the police to come and take daddy away when he's angry and when he fights him.This is the first time he's ever said anything like this but it was an incredibly calculating statement. He wasn't in hysterics and carefully chose his words. My son knows the police take away the bad guys, and for him to say that to me coupled with all of the previous issues I've had with his father as led me to believe my son is not safe with him. I won't put my son in a situation where the police have to be involved.I spoke with his father to tell him what my son had said. The father told me he did get mad at him because every time my son comes over he ends up throwing a tantrum. No matter how many times I've explained its because he misses him and thats how he thinks he'll get something from his dad, he just gets so frustrated and lashes out. This time he fully admitted to what he did. I tried figuring something out while being firm on my point. All his father said to me was "whatever".I just don't want to lie to my son. I'm not trying to speak ill of his father and paint him to be some kind of asshole monster, but I don't want to lie and pretend that his awesome dad just up and left for no reason.How can I explain depression to a child? The last thing I want is for my son to think this is his fault. via /r/Parenting http://ift.tt/2oCiPMN