Jeff,
The reason Avast stops the scan is to prevent any further damage if "infection" has begun to spread.
This is the safest way to handle a possible infection.
Avast also allows you time to look at the file and determine if you want to delete it or not.
You can set the Standard Shield to Perform "silent" action if you wish, but then you would not know "when or what" action Avast was taking. Not a good idea.