It's easy , all they have to do is walk into a gun store and buy one off the shelf after showing ID in most states and in any state they can just buy one off a private seller with no ID at all or have someone else buy it from the shop and resell it . It's not like any of those weapons are registered or trackable . As shown recently even someone on the no fly list as suspected terrorists can buy a gun legally with no effort.
Guns are simply inanimate objects with the capacity to kill. The same can be said of cars, knives, pots and pans, etc. Terrorists and criminals aren't dissuaded by dragnets which disenfranchise the rights of law-abiding citizens in hopes that criminals will be stopped in the process. They most likely laugh at such initiatives and revel in the opportunity that is created to wreak havoc on helpless citizens.
I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.