If I'd found my DH/DW having slit their wrists and thrown themselves out a window into the snow, after months of mental health issues, I would most certainly assume they could've (probably would've) killed the children.
If they'll do that then they're in a state where they could do anything - and I've read enough cases where the parent kills the children and then themselves to think it's very likely, especially as they did it while home alone, in sole charge of the children, instead of leaving the house to do it while the children were in care of someone else. Given those factors, I'd immediately fear the children were dead.
And yes, I know it was a fully furnished part of the house...where an 8 month old, 3 year old, and 5 year old were shut up alone and unsupervised, having just been in the care of a woman who had tried to kill herself, and nearly succeeded. I would not be waiting with her until the ambulance arrived, not knowing whether or not my babies were okay.
Frankly, I'm shocked that people's first thoughts wouldn't be 'oh my god, what did she do to the kids?'