A critical (or traumatic) incident is any event outside the usual realm human experience that is markedly distressing (e.g. evokes reactions of intense fear, helplessness, horror, etc.) Such critical incidents usually involve the perceived threat to one's physical integrity or the physical integrity of someone else. Most importantly, critical incidents are determined by how they undermine a person's sense of safety, security and competency in the world. This results in a form of psychiatric injury, also called traumatic impact or traumatic stress.
Examples of Critical Incidents
Individual/Personal
Automobile accident, or any accident involving serious injury and/or property damage
Industrial accidents involving serious injuries or fatalities
Sudden or unexpected death of a relative, friend or colleague
Sexual assault/abuse
Robbery and violent crimes
Domestic violence
Child abuse and/or injury or death of a child
Psychological/emotional abuse
Suicide or attempted suicide
Homicide(s)
Line of duty death or injury among emergency/law enforcement personnel
Any life threatening experience
Adverse/negative publicity
Observing or being aware of unethical acts
Observing any of the individual or community critical incidents
Community/World
Fires
Floods
Earthquakes
Hurricanes
Tornadoes
Multiple injury/fatality accidents
Large scale environmental pollution
Terrorism
Acts of war
Child related traumatic events
Homicides in the community
High publicity crimes of violence or sex
Community disasters
Being an emergency worker/first responder in critical incidents and disasters (Police, Fire, EMS etc)
As you can see, you need not be directly involved to be adversely affected by a critical incident.. Generally, the closer you are to the actual event and the people involved, the more severe the impact. However, television and news media coverage, especially excessive and/or graphic depictions, may serve to increase the likelihood of experiencing traumatic impact, especially anxiety and feelings of not being safe.