Threats derive from a complex number of sources that may trigger violence. These may include policies that some employees find objectionable, such as a bad performance review or constructively intended criticism; rivalry or disagreement between employees; failed or drama-filled romance with a co-worker; and stressful or discourteous interactions with customers (who may themselves be sources of violence).
“…employees have benefited from stress-reduction classes or lessons in tactics to diplomatically handle difficult people…”
Most commonly, the violent act is undertaken by a terminated employee who becomes disgruntled and feels there is nothing to lose.
    Prior to making any new hires, an employer would be wise to assess the risks and set up relevant policies that at least address the most common threats. This evaluation might begin with an assessment of the premises. Sometimes the most serious threat is external. Depending on the type of business they conduct, employees may routinely expect to handle contentious or emotionally distraught customers. Other workers, perhaps those who handle large cash transactions or valuable merchandise, may be targets of robbery.
    Short of creating a high-security compound, employers can take some precautionary measures in these cases. Mitigating features can include alarm systems, security cameras or guards, an employee-controlled buzzer on the entrance door and even bulletproof glass.
    Another approach that may be less obvious, yet is effective, is for employers to train employees on how to avert bad situations. For instance, employees have benefited from stress-reduction classes or lessons in tactics to diplomatically handle difficult people.
For more:Â Â http://www.workforce.com/section/legal/feature/employers-prevention-workplace-violence/index.html