Gun Free Zones?

If a sign is posted that a building, business, area or premise is "gun free", why can't a lawsuit be filed when someone is gunned down in those areas? If a sign is posted which states that it is a "gun free" zone and yet people are shot and killed...

Perspective...

There is a story of a man and his Son who went fishing. They spent all day out fishing but caught nothing.    Later that evening the man wrote in his diary that it was a terrible day. He wrote how he and his Son had fished all day long but...