I'm waiting to hear more detail on some of these allegations and I would really like to hear the father's version too. For instance, it just "might" be possible that they parked at Target and the father ran in to get something while the mom and kids stayed in the car. Maybe (just maybe) the mom thought he was taking too long and made the decision to take her daughter in with her to look for him, leaving the baby in the car. "Maybe" leaving the baby in the car was not the father's decision at all and she did it after he was gone. Ok, odds aren't real high, but still, possible until we hear the details.
Due to being up close and personal with a loved one having Postpartum Psychosis along with Bipolar, I know only too well how scary it is for the endangered children. One cannot be forced to continue treatment, even after involuntary commitment and many sufferers learn how to maintain the semblance of normalcy for short enough periods to fool the casual onlookers. Even CPS workers count as casual onlookers when they only drop by to check off the standard questions on the forms and rush off to their gazillion other cases.
The mom being mentally ill doesn't make the father necessarily a saint either. But I'm giving him the benefit of the doubt until we know more. At this point, knowing of her mental illness, I know too well that every accusation she made COULD be false. I hope she didn't kill his son.