If a policeman was called to a car crash, that would be an accident.
If he is then called to break up two men fighting, that would be an incident.
The first is an unfortunate chance event, the second is just an event that he must deal with. So the policeman spends his day responding to incidents, but only some of them are accidents.
So what if he receives a report of a drunk being a nuisance in the shopping mall? accident or incident?
Its an incident.