When the agressor is no longer a threat you no longer have the right to shoot. The purpose of the initial shot is to stop the agression.
If the attackers continue to threaten you with a weapon you can stop them from further attacks.
This looks like murder.
I'm sure that is exactly what those whom lives are in danger and reacting accordingly, are standing there thinking.
"Hmmmm, are they still a threat?" If they're still breathing then yes, they are.