Murder is illegal. Attempted murder is illegal. Trespassing is illegal. Possessing a firearm while committing a crime is illegal. Carrying a firearm on school grounds is illegal. The criminal background system failed. Law enforcement was incompetent and derelict in their duty to serve and protect. If ALL these laws, procedures, and measures failed, exactly what do you think more laws are going to do to stop another mass shooting. Seems to me that we need to start enforcing the laws we already have and hold incompetent people accountable rather than violate the Constitution.