@stux custody disputes where one partner is obsessed and violent are awful, and it's hard to know if intervening helps. Had something like that happen many years ago where one of my neighbors was trapped in the parking lot with her kid while her ex screamed at her. I ran him off and he came back a few nights later, pounding at her door wanting to be let in. Called the cops and stood there filming until he ran off. A few days later, he kidnapped the child. Eventually she got the kid back but :-(