this isn't the first time in U.S. History that bad people wanted to hurt the United States. The important question is whether we're willing to descend into Fascism to solve short term problems. The problem being Islamic Terrorists that still haven't killed as many people in the US (in the last decade) as generic angry white boys.
If the entire country is willing to repeal the 2nd amendment then we can do that. It's a bit silly to have a murder weapon as a right, when driving a vehicle that you're dependent on for your livelihood is considered a privilege. But you can't stomp on constitutionally protected rights out of convenience, because that puts free speech, Freedom of religion, and right to a jury on the chopping block as well.