Write a newspaper article about Gatsby's death.
I cannot write an article for you, but I can advise you as to how newspaper articles are written. Good journalistic practices are very different from the way we write essays.
First, newspaper reporting always starts with the present and works its way back. So, your "lead" must be Gatsby's death. Then you can begin to tell the "back story."
Second, your story must tell the reader who, what, where, when, and why. If it is possible to get all or most of this in at the beginning, that is the best way to do it. For example, a first paragraph might contain this:
Millionaire Jay Gatsby was found dead in his pool today, in West Egg, Long Island, murdered by George Wilson, garage owner and jealous spouse.
Third, you will notice that my example paragraph is just one sentence in length. This is permissible in a newspaper story. People want to digest their news in very brief paragraphs, unlike in academic writing, where full development of a topic is expected. As you develop the "facts" that led to Gatsby's death, use short paragraphs to do so. One paragraph might consist of a quick biography of Gatsby. Another might consist of a description of the crime scene. Still another could be an interview summary with one brief quote.
Finally, you should always be able to provide a source for your information and credit that source in your story. You might have interviewed Nick, for example, or a distraught Daisy Buchanan. Tom might have had a few words to say about Gatsby. You might have gotten some information from the local police. Some of those party-goers might have something to share about Gatsby, too. No matter what your sources are, a good reporter shares them.
This is a great assignment, and I hope you have a good time doing this. Journalistic writing is a good skill to have.