I understand exactly what was probably going through your head OP, i had a similar experience a while back but not involving a child.
I was driving down a road where i am from and around 100 yards in front of me a middle aged woman was crossing the road with her dog, i little terrier type, she then continued up a street just off the road i was driving along.
Now as i got to where she crossed a bloke came walking the opposite way up the road i was driving down, also walking a dog, the dog was a pitbull type and he was what as i would describe as a U WHAT M8 type, the dog was yanking his shoulder out of his socket and foaming at the mouth, looking very aggressive etc and walking approximately 50 ish yards behind the woman with her little dog.
So i am thinking to myself if she stops for some reason then the guy and his dog will be very close to her and i just had an image of her dog and possibly her seriously injured if that pitbull gets anywhere near her, so i turned up the street and caught up just behind her, she looked around at me so i said, hi, i am just making sure you get where you are going ok, me presuming she had seen the pitbull around 50 yards behind her, she looked at me funny and about 20 yards further she opened a front gate to a garden and on into the house, i thought ok great, atleast she is home and I thought nothing of it again and continued on.
I stopped at a co-op shop further down the round and it was busy so i was in there around ten minutes, when i came out there was two police cars around my car and 4 police officers, i thought wtf, i walked over and one of them said is this your car, i said yes, as soon as i said yes i was cuffed and arrested and in the back of a police car.
So i asked one of them in the car what have i done, she said a woman had phoned 999 and reported that she had been stalked by a man and gave them my car reg etc, i was sat there in shock
In the end i told them what i was actually doing and the woman came down with an officer and they told her what i said, she only believed the story because she said as she was looking through her window and on the phone to the police she said she did notice a guy walk past her house with an aggressive looking dog.
So, never again will i stop