While it is impossible to weed out all workplace violence, there are things employers can do to educate and their managers on recognizing the warning signs before tragedies such as the Annie Le murder.  According to Environmental Health and Safety Today, these warning signs include changes in mood, personal hardships, mental health issues (e.g. depression, anxiety), negative behavior (e.g. untrustworthiness, lying, bad attitude), verbal threats and past history of violence.  I would have created a great list for you, but I found the suggestions from Environmental Health and Safety Today to be very inclusive. These suggestions include:

1. Management should conduct a thorough organizational risk assessment and develop workplace violence prevention policies and programs that address potential risks in environmental design (security cameras, key card access), administrative controls and behavioral strategies.
2. Programs should clearly define the spectrum of workplace violence (ranging from harassment to homicide), delineate employee responsibilities for recognizing and reporting signs, and be shared with every employee. All programs should promote zero tolerance.
3. Ask for and integrate employee ideas when developing and implementing a violence prevention program.
4. Create a confidential and seamless reporting system. Encourage workers to report any and all concerns to a single representative, such as an occupational health and safety professional or human resource manager.
5. Incorporate a variety of communications tools such as posters, newsletters, staff meetings and new employee materials.
6. When training employees, review common warning signs, behavioral traits and how to recognize potential problems. Employees should also understand that each case is different, and to not limit at risk behavior to a standard profile.
7. Involve all employees in workplace violence prevention programs. Training should be ongoing and mandatory for every employee.
8. As an employee, actively participate in all education and awareness programs. If you do not have a violence prevention program at work, request information from your occupational health department, human resource department or manager.
9. As an employee, if you recognize that a colleague exhibits at risk behavior, report any concerns to your human resources representative or occupational health professional.

Lastly, I think it would be prudent for large organizations to pay for a service to run conviction record on all current employees each year.  Smaller organizations may want to hire an intern to look up employees on their state’s public convictions record database (which are almost always online). Employers would be surprised to find that many of their long term employees have several convictions ranging from drug trafficking to felony assault.  You will want to decide in advance how you will deal with employees who are convicted of drug related or violent crimes.  This will be your hardest task in this equation.

When reviewing past cases of workplace violence, it often seems that there are numerous warning signs that people notice, but never report.  An employer should do everything in their power to protect their employees.   The most powerful thing they can do is not beef up security or add cameras, but add awareness and provide access to confidential reporting of suspicious behavior.