If nobody died from this it is a good outcome. Hopefully the people hospitalized will be ok. The ammonia used for this application is around 98% ammonia. Just as a reference the ammonia you get from a store is about 5%. Although the liquid is very dangerous and can cause burns the vapor is even worse. The vapor attacks any moisture including the lungs. Once in the lungs the the vapor condenses back to liquid which drowns the person. The liquid is normally under pressure and is a refrigerant so it will continue to flash into vapor for awhile. The best thing to do in a situation is to get upwind of the leak and keep distance.
He speaks truth. Start looking now.