Accidents and incidents do happen at work. No not-for-profit is immune to it. Here is a template of a comprehensive incident report that you can download an re-purpose for your organization. As a risk management initiative, incident reports help mitigate some of the aftermath of an incident/accident as well as dealing with the liability issues and insurance.
Incident reports capture on document the exact details of what happened. It should ideally be completed while the details are fresh in the minds of those who witnessed the incident/accident.