Reacting to the Florida school shooting, Sen. Richard Shelby (R-Tuscaloosa) Tuesday said he wants stronger background checks for gun sales. President Donald Trump also has called for an overhaul of the system used to screen potential buyers. Pointing to the failure to investigate the accused gunman, despite warnings, Shelby said authorities must follow-up on any threat. He says people who use guns to commit crimes should be "severely punished." Shelby made his comments during an appearance in Huntsville.