The guns used were illegal, as is any weapon taken onto school property in Connecticut. The weapons didn’t belong to the shooter, they belonged to his first victim – his mother. Murder is illegal, as is suicide in most states.
People want to pass new laws, while there is no funding for enforcing the existing laws. They want to believe it will make a difference. They want to do something.
Pass all the laws you want, but don’t realistically expect anything to change until the American society is healed and healthy again.
With few exceptions, every man in Switzerland between 18 and 55 is a member of the National Guard, and has been issued a military assault rifle, that they keep at home. These incidents don’t happen in Switzerland. Switzerland has a healthy society, so people don’t reach the level of despair that results in these events.
Back in the 1970s we started to see ‘suicide by police’, people would set up a situation where they knew they would be shot by the police. This a variation on the same theme. People have decided on suicide and want the world to know about. The news media obliges.