How does the US Government curb mass shootings? What constitutes a “mass” shooting?

What are some solutions to help with this occurrence? Do you foresee any problems with your solutions? Should there be a federal law or should states create laws for their own states? What laws are in place currently or have been in place in the past? Were they effective? What would the consequence be for attempting or participating in a mass shooting be? Does age factor in? Is there parental accountability? Are mass shootings a current problem that needs to be addressed on a large scale or does the media make them seem more prevalent than they are?