Others seem obvious. Many contradict at least one other on the list. Parents should pay more attention to what their children are doing in the garage with steel pipe, nails and detonators. Law enforcement should investigate if they get complaints about boys building and testing pipe bombs. School administrators should notice when a group of students refer to themselves as any kind of Mafia.
Guns are too accessible.
We need more gun control laws. Gun laws already in place were broken. If teachers had been carrying a few concealed weapons to defend themselves and their students, this wouldn't have happened. Gun control laws endanger the public. There is too much violence on television.