There's no other way to do it. Adam Lanza had access to guns that were obtained legally. Even limiting the kinds of guns that can be sold won't work; a shooter can do a lot of damage with several revolvers.
We have to have a repeal of the second amendment. We have to do it in a way that doesn't jeopardize the rest of the constitution. We have to revise our vision of the future of humanity. We the people disagree with and are diametrically opposed to our forefather's characterization of and understanding of guns. We the people recognize that a new age of guns has dawned, that simply revising an interpretation isn't good enough, that the future of humanity is a future without guns.