How to write a fictional news paper inside a book?

Read the book In Cold Blood. It is based on a true story, the murder of a farm family by two former prison cellmates. Truman Capote wrote it and it is considered to be the first 'Docu-drama' meaning a true story written in the form of a novel. It is a very well written book. Maybe you can find someone else to help you with the fictional news story. Maybe that skill is not in your wheelhouse. Or just write the news story quickly to get something down on paper and then have someone look at it to give you some feedback on how to improve it. News stories are more factual, meaning they answer the questions: Who? What? When? Where? Why? and How? They deal in facts, not in emotions. Start with the facts of the case and then put those into a news story.

I would recommend studying some news paper articles and taking notes on their key characteristics, such as their voice and diction. Rather than writing in your normal style, pretend as if you are writing an essay- use some inflated vocabulary, keep a somewhat flat tone, and try to refrain from including too much apparent bias (unless it serves purpose to your story, such as if the intentions of your character are misunderstood by the public).