Imminent Threat
The above procedure is a more or less “business as usual” approach which considers the application of a protocol to a potential problem, but one that may be (hopefully) handled in a civil way without a physical confrontation.

If, in the above scenario the situation begins to deteriorate and/or if right from the beginning the Problem Customer appears to pose an imminent physical threat, different actions are called for.

As the potential for a physical confrontation escalates, staff need to drop any pretense of worrying about not disturbing other customers or “managing” the situation. The activity prescribed below calls for training and “drills” to overcome the natural tendency on staff’s part to not create a disturbance in the Library.

If you believe the customer will become physical and appears to pose an imminent threat..
And if the customer appears To be unarmed….

Immediately call out in a loud voice “Call 911”
Repeat until assistance arrives.
Upon hearing “Call 911” one staff person will call police/security.
All staff hearing “Call 911” should immediately move to the vicinity of the area of alarm. (Swarm)

The purpose of this emergency procedure is to immediately signal your need for assistance to all in the vicinity...customers and staff alike. It has also been observed in law enforcement scenarios the presence of many people converging on a scene tends to disconcert and give pause to a person contemplating an assault.

The exception to the above action, however is an important one. If the staff person knows or has reason to believe the Problem Customer is armed, a different response may be necessary:

If the Problem Customer is armed….

Remain calm and comply with customer requests.
Ask the customer to put the weapon away. It is not needed.
Attempt to signal alarm through personal alarm device or through other non-explicit means.
Attempt to move, if possible, to a more public area or where staff are congregated.

Obviously, this type of situation is one none of us hopes to ever be involved in. If your staff ever are confronted, however, it will be important for them to remain calm and respond appropriately. Years in the military have persuaded me that people return to their training in a panic situation..if their training has been consistent, thorough and recent enough to be memorable.