don't know what to do.

Rebecca • Just a mommy enjoying life :)
So I was at work and my parents sent me a text saying come home right now. I live with my parents my fiancé and our 2 kids one is 2 and the other is 8 months. Now I see that I am thinking ok great with did he(fiancé) do now. He doesn't like to watch the kids he even tells me. He doesn't like to be a parent. So I get home to find out my 8 month old was dangling from the swing only thing holding him there was the waist straps and my 2 year old just sitting in the living room by himself. He just went upstairs to sleep without asking my parents if they can watch them for a little till I got home. So my mom told me my 8 month old was screaming at the top of his lungs in pain suffering cause he couldn't pick himself back up. He has little red marks on his upper thighs from it but it should go away I hope. But idk how to handle this. If I even say something I know he will just get defensive and not listen. I don't want to start a big argument and have even more issues arise. I would like to converse calmly so he understand and maybe solve the problem but idk if that's worth it since he doesn't care. I am torn sort right now that he doesn't care about our kids. Any ideas on what I should do !! :(