Gregory served over 37 years as a firefighter and has more than 30 years of experience as a fire and arson investigator. He has conducted both criminal and civil fire investigations, and has testified as an expert witness in fire origin and cause. Gregory holds an Associate Degree in Fire Science and a Bachelor Degree in Fire Administration with an emphasis in Fire Investigation from Columbia Southern University. Gregory is a Certified Fire Investigator (CFI) by the International Association of Arson Investigators and Certified Fire and Explosion Investigator (CFEI) by the National Association of Fire Investigators. In addition, he is certified as both an Arson Investigator and Fire Investigator by the Office of the Illinois State Fire Marshal. Gregory is a Certified Fire Inspector I and Chief Fire Officer with the Office of the Illinois State Fire Marshal.