I would not be surprised in the slightest if what happened was the mother walked in with the two children assuming the older one brought in the baby. When within a short time she realized the older one assumed the mother took the baby, the mother went running out to get the baby. By that time the passerby who saw the baby moments after the mother left had already broken the window and called the police who arrived within minutes. So the whole shebang took place within 10-15 minutes.
But of course the above scenario doesn’t sell papers. And then the passerby can’t pose for the media as a hero. And the press would barely have a Page 17 three line burb rather than a Page 2 five article hitjob.
And if the above scenario was indeed the real story while the press ran with some fiction it wouldn’t be the first time. Or second. Or five thousandth.