Clever child

Bill and Marla quarella, but he didn't want to let their 10 year old son listen to, so they asked him to go out to the balcony and said:

-You stand here and inform us what was happening our neighbour's?

The boy stood on the balcony and started to "report":

-A driver stops in front of our neighbour's door:

-...

-An ambulance passes!

...

Mr and Mrs Andersons are also quarelling.

Bill and Marla were started, stopped quarelling and turned to ask their son:

-Why do you know that they are quaralling?

Because Tom, their son, is also standing in the balcony!