The first source of variations in media reporting of one event lies in the type of journalism that is being conducted.
On scene journalists will go to the scene of the event and will work to collect and to verify the accuracy of as much information as possible. Then they will attempt to write the most coherent and comprehensive article that is possible, and to meet very tight deadlines.
On scene journalists will interview witnesses, officials and others in the heat of the event, then get background information. Then they will format a story that will be seen by an editor, fact checked, then read off of a teleprompter by a television newsreader, sent to the major news feeds online, or end up in the next day's online or print newspapers.
Television journalists will have their spoken summaries and interviews in front of a camera, with visual presentation of the journalist, the witnesses and others and of the event as the most important elements. Television news will solicit and obtain as much visual imagery of major events as is possible from professional, amateur and archive sources.
Investigative journalism will take the fullness of time, with true professional interviewing, detailed research and extensive fact checking as part of the process.
Scientific journalism is a new specialty in journalism, requiring skills at dealing with the complexity of the scientific issue as well as the complexity of competing arguments about the issue that go on among members of the scientific community. Scientific journalists are best served by having specialized knowledge as well as long time or special connections to the members of the science community, often within sub specialties of science as their focus.
There are other specialties of journalism that require a long time for establishing sources, connections, experience and knowledge. Political journalism, military journalism, and crime journalism are examples.
Citizen journalism is fraught with the cognitive errors, filters and biases that the citizen journalist may or may not have overcome. Citizen journalism, however, is less susceptable to external bias and will present fresh and unique perspectives that can draw great audiences.
The wide variety of differences in reporting on the same matter, issue, event, or interest simply comes from the orientation, background, knowledge, skill and biases of the journalist.
The second area of variability in reporting of the same event or issue lies in the format or presentation of the news. Format orientation will change what is presented or covered. The format comes with external and internal biases, some of which are covertly imposed by major advertisers, and others which are imposed by assumptions that maximize audience, which maximizes profit from advertising.
Other biases or focuses can come from political agendas and personal biases, limited time and presentation formats and overall styles of various "newstainment" shows. Also, optimization programs that tell the networks which stories are getting the most attention from the online audiences. This is a form of bias that is based on popularity among a subgroup of society.
Then, there is the matter of the infamous "news cycle". These days, the news stories hit the web. Then the major news organs pick up the story. The bloggers read the early news. The search optimization engines, particularly Google and Yahoo spit out the hottest and most viewed stories. The bloggers pick up the stories and generate articles. Over a 24 hour period, there can be several news cycles that go on for a few hours before they peak.
Or, there are week long or month long news cycles, again based on search optimization or editorial decree. These go on as more and more information is gathered, guests are scheduled for news shows, and facts are checked. One news issue, person or event can dominate the news, die out, then come back again and again, as with a major celebrity who has been involved in scandal, goes to jail, goes to rehab, is hounded by paparrazzi, goes to court, and so on.
The major decisions to ignore the abduction of some children while obsessing over the missing, blond, attractive woman for months are incomprehensible to many, even if both stories would be equally compelling. Race, economic standing, the activism of the community, and the media savvy of the relatives and community, are only part of the equation. The bottom line is the assumption that the audience will be larger and far more interested in one race over another and in the wealthy or famous as opposed to the poor and unknown.
The biases and filters of the on scene journalist have been captured on film and probably be captured again and again. The on scene "journalist" who refuses to speak to anyone who represents one ethnicity of witnesses while talking only to those of another ethnicity is well known and has to do with audience share rather than obtaining fact.
Witnesses are remarkably wrong, have differing perspectives, and will rarely agree on what it was that actually happened during a fast moving sequence of events. Different stories can come from each of many people who witnessed the same event.
As a result, one journalist may include some statements and follow what those statements lead to, or may ignore the same witnesses and watch the story unfold later, as those witnesses are heard by someone else. In some cases, the entire existence and statements of some witnesses will be deliberately suppressed by one news organ and included by another.
There is information suppression, information obsession and information "handling", where the facts can be twisted or distorted in order to further an agenda. Various reasons exist as to why some information is left out and why other information is given extensive treatment. there may be doubt or bias as to whether the facts can be confirmed or whether a witness is reliable.
There may be profit in and bias toward making up information and attributing it to "unnamed sources" who do not even exist. There may be real unnamed sources who would be in serious jeapordy if their identity were revealed. There might be a sociopolotical agenda that is imposed and supported by presenting false or distorted information.
The solution to the problem of variable presentation of fact is simple. A good bookmark collection of news aggregators and rss feeds, combined with reading multiple sources that have good journalistic reputations, and reading blogs that are written by reputable and competent bloggers will help to put just about any story into a comprehensive, factually oriented, less biased and more accurate perspective.