The interviewer would like to know more about the types of situations that you have had to deal with, on the job. If you have ever had to deal with an assault or violent situation on the job, take some time to walk the interviewer through the steps that you made. The idea here is to give a brief overview. Avoid going into too many details; thus, losing the attention of the interviewer.
If you are newer to your career or have never had an experience like this, take some time to talk to the interviewer about what steps you would make. Since you may not have training in this, rely on your instincts.