So, how damn hard was it to say that the first time?
What can be done about the problems with gun crime.
1) Change the way people vote. Right now the FPTP system is destroying the US, politicians are often in it only for the money, and they're taking the money and representing money. People don't have a real choice, people don't have a chance to say what they think. If you don't support the Republicans or Democrats you're doomed to fail, no matter the outcome of the election.
In Germany, with PR, the third party didn't exist 10 years ago. While the US has flirted with Libertarians, Socialists, Tea Party and the like, Germans actually get to vote for what they want, instead of it being like a mole in their face. The AfD got 12.6% of the vote, because people felt they could vote for them, unlike in the US. And the AfD will have an impact on the policies that come out of the government, even if they're not in it.
2) Change the "can't do" mentality in the US. Change the lack of desire to solve problems.
3) If you want to be more specific about guns, then there are plenty of things that could be done. A lot of them would have people screaming and shouting about their right to own weapons.
4) Change education, make education something that can change communities, change people's lives.
Without number one, nothing else is going to happen. No change will happen. Number one isn't going to happen because the rich control the government and really don't want to lose their ability to do so. Do they care if a one year old kills himself? No, they've got a massive yacht, loads of houses, enough money that they only need to worry about getting some disease that can't be cured.