You really do want to keep digging...
"Woman walked onto the crossing in front of her, then 'spotted' the ambulance & stepped backwards - leaving the dog on the end of the lead. "
So at one point there was a person and a dog in the path of the ambulance.
Will you either get it right or shut up?
I wonder what would have been said if it were a horse.. you can't use sirens when approaching a horse as it may startle them.. come to think of it they startle dogs too.