Personally, I would like to see Trump offering training and limited deputization to a recognized force of militia across the United States. After 40 or 80 hours of training, issuing a Federal Agent identification and authorization to concealed carry in that capacity. An added bonus would be to provide a Beretta M9 and a Colt M4 assault rifle to each individual along with an Arsenal size amount of ammunition. Put a few thousand of these special agents in all of these anti-gun cities and states. The only duty of these unpaid federal agents would be to be armed and prepared to act in the case of a mass shooting.
I think Zero purchased a large amount of ammunition and handguns for his force of weaponized IRS army. Trump should disarm every federal employee which is not a law enforcement employee. These weapons and surplus of ammunition could then be distributed amongst law-abiding American citizens such as the above stated special agent. That would be one way to make sure that there are concealed carry by law-abiding citizens in Chicago in Los Angeles, and every metropolitan area where gun crime is a problem. This could be part of his initiative to reduce mass shootings and crime.