SAN ANTONIO - A massive collaboration across the San Antonio region has first responders constantly training and preparing to keep us safe. We saw that collaborative effort firsthand last month when a man killed his neighbor, set his house on fire and opened fire in the neighborhood.Seeing that incident prompted KSAT to look further into how that seamless teamwork happens. Part of it is in great part to an enormous, special training exercise combining hundreds of people from agencies local to federal. KSAT got an exclusive view of that training in 2017. Preparation for mass casualty events translates to smaller scale situations, like that response three weeks ago to an active shooter in south San Antonio three weeks ago.