The dumpster on fire

Imagine the following scenario: A Walmart in your town is open for normal business on a Saturday afternoon. While unpacking boxes in the stockroom, an employee discovers that the dumpster connected to the building is on fire. The dumpster is used by Walmart’s employees, as well as a contractor who is putting a new roof on the building. Fire Engine #1 from the local FD responds and extinguishes the fire. You are the Fire Investigator assigned to find a cause and origin. List four different people you would like to interview and two questions you would ask each person. Explain why these individuals are important to interview.