I worked in a small private hospital in New Jersey. They already knew I was an O negative, universal donor. A fireman was injured and needed a lot of blood. He was a rare type. They came into my office and asked how long it had been since I had given blood. Then they offered me cookies and orange juice. That was always the clue that they needed me.
It was not until the next day that I was told that I had saved his life. If they had had to wait until the right type of blood came from a major hospital or Red Cross he probably would have died.
Later that week I helped out when lots of the local policemen and firefighters came in to donate replacement units for him that it got really funny. All these big brawny, brave men were passing out left and right. It actually got to the point where we were stepping over the ones on the floor to take care of the ones still on beds.