In the wake of the movie-house massacre in Colorado last week, both presidential candidates did the right thing.

This was not a time to dust off pre-constructed programs tucked away for the just the right tragedy. It was a time for just what both President Barack Obama and challenger Mitt Romney did, which was to put politics aside and express sympathy for the grieving families.

It was time for a moment of silence.

It’s a cliché to say that a tragedy such as this, or shooting rampages at Columbine, Virginia Tech or Tucson, Ariz., provide opportunities for a national conversation about violence in our society. Having a meaningful discussion in the heat of the moment, however, is difficult because the acts are too singular, their perpetrators too twisted, the circumstances too bizarre.

The moment of silence, however, will come to an end, and there will be a time when the broad discussion about public policy should begin.

The topic of these conversations should include whether we are doing enough to keep the tools of mass murder out of the hands of mentally unstable people.

The question is not whether Americans have the right to bear arms. Of course we do, but the question should be what limits are acceptable.

We already ban fully automatic firearms and artillery pieces. What rationale allows those limits but permits the legal sale of semi-automatic weapons with high-capacity magazines? When does the purchase of large amounts of ammunition become a matter of public concern?

Until last Friday, the Aurora, Colo., shooter was, by all accounts, a law-abiding citizen who used legal means to arm himself. He was shielded by the same laws that the vast majority of gun owners use to protect themselves, as is their constitutional right.

It would be wrong for us to accept this latest murder spree as an unfortunate cost of living in a free society. If a dozen people had been killed by a terrorist last week, we would know what to do. Americans would feel that they were under attack, and would want to protect themselves.

There may not be a solution that would completely prevent another event like from this ever happening again, but we should at least talk about ways that could make them less likely or less lethal.

This may not be the moment to have that conversation, but it should come soon.