HR doesn't like the idea of employees performing sweeps of this nature, but our Security Officer said she thinks local law enforcement may require it to give the building the "all clear."
Your employees should be trained to be aware of their surroundings and observe if any foreign objects/containers/etc. are present that don't belong, and relay their observations, through the SO or other bank-side event coordinator, to law enforcement. But they are not, in all likelihood, bomb experts, and should not be asked to act as such.
What your SO is suggesting is completely backwards, and HR is right to push back on this point. The notion that bank employees, who are not subject matter experts, should determine that it is safe for law enforcement (some of which who are
subject matter experts) to enter is illogical.