I think the age that one must reach to buy a gun shouldn't be lower than 24. It seems to me that most random shootings are done by people below this age. I also feel that one should pass an IQ test, and a mental evaluation before being allowed to purchase a firearm. Most criminals also get criminal records before that age, and will disqualify themselves from owning firearms. This will solve the gun crime in the US, while also preserving the rights of responsible adults.