Using lethal force against drug smugglers likely won't be very effective, they'll find some other way to smuggle drugs and get them to their customers. They always do.
I don't know the reasons behind this particular action but it may make sense from a larger perspective, to include messaging. But if it becomes a more common thing the risks for mistakes and miscalculation rise significantly and the
killing innocent folks like this becomes much more likely. Even Tom Clancy realized how messy it could end up getting.