It would be interesting to see the footage before they turned the corner.
The boy is following a woman pushing an empty pushchair, so surely if you had GOOD intentions that would be the first person you'd approach to see if he was yours?
But if he didn't have good intentions, it's incredibly brazen/high-risk to take someone so close to a parent. So maybe he didn't see the parent.
It's baffling and quite terrifying really.