How should I start off my mystery story? and why is the church vacant? PLEASE HELP?

For a school project, we have to write a mystery story. My topic is when a girl (Candra Morris) is walking in the park and notices a hidden path that leads to an old, but beautiful church that has been vacant for years. Candra wants to investigate why it is vacant. I'm not sure how I'm gonna write about why the church is vacant so can you guys PLEASE give me some examples? I'd really appreciate it and also how should I start off my story?