Gov. Rick Scott on Friday offered a $500 million proposal to address school safety, gun laws and mental-health issues after the mass shooting this month that killed 17 people at Marjory Stoneman Douglas High School in Broward County. The proposal, in part, calls for at least one school resource officer to be stationed in every public school in the state. It also calls for requiring that people buying guns be at least 21 years old, a requirement already in place for handguns but not long guns.