Being a bystander is similar to witnessing something, it is a person who does not directly experience an event but is there at the time.
Witnessing an event can have a number of differing effects on a person and can depend upon an individual as well as the individual circumstances of the event.
Sometimes witnessing an event can have similar effects as the person who experienced the event.
In some instances this can lead to what is known as post traumatic stress disorder(PTSD).
Similarly when supporting someone who has experienced a traumatic event, hearing about the event can have an effect on the individual called vicarious or secondary trauma. This can lead to a range of mental, physical and emotional problems being experienced.
More information about PTSD and the effect of secondary trauma can be found from PTSD UK.
There is an NHS leaflet which aims to help people who have been affected by a major incidence and the websites below also has information about how to cope following a traumatic event, and how to support yourself and others. This includes talking through the event, listening without judgement and putting in place self care, like being active, eating and sleeping well.