Someone claiming to be the lawfully-armed citizen was posting on the Journal Sentinal [local paper] story about this.
He said he didn't see the sign (which I can completely believe),
he has a license,
he was carrying concealed,
the thug was holding the shotgun to the head of the clerk,
then pointing it nervously at customers,
he evaluated what was between him & the thug, as well as what was behind the thug, & decided it was safe to shoot.
He also says he was told (? by police?) that the robber was hit twice.
This has another thread in the WI forum, as well as being in the "no need for a gun?" thread there.
Yes, several of us have already emailed Aldi pointing out that their sign didn't stop the criminal, but might have resulted in the clerk being killed if the lawfully-armed citizen had seen it & gone elsewhere.