People who own guns should keep them locked up. In my opinion, those who believe in a literal hell are less likely to kill others than people who don't believe in a literal hell.
An NRA spokesperson said that each school should have an armed guard but I don't believe the public should pay for this. There should be a violence tax on violent movies, games and TV shows to pay for this.
If this isn't possible, poor districts could train their school secretaries to shoot a handgun, which should be kept in a locked drawer. Each secretary could also be given a bulletproof vest with "school employee" printed on both sides. The secretaries could also be given bulletproof helmets with clear bulletproof visors. Then if a gunman starts shooting in room 7, room 8 or 6 could lock his/her door and call the office and say, "Gunman in room 7."