April 20 will mark the 10th anniversary of the massacre at Columbine High School in Littleton, Colo., where Eric Harris and Dylan Klebold shot 12 students and a teacher and wounded 23 others before turning their guns on themselves.

In years since that day, shootings like the one at Columbine have become common. Anyone who’s been watching the news in recent days can’t deny that.

On April 3, a gunman killed 14 people at an immigration-services center in Binghamton, N.Y. On April 4, a man wearing a bulletproof vest shot three police officers who had knocked on his door in response to a report of a domestic disturbance. And, on April 5, a man who had discovered his wife was leaving him shot his five children before taking his own life.

It’s disturbing that gun violence has become such a staple of our national news diet that, 10 years later, our national conscience is as numb to the tragedies as ever. But what’s even more troubling is that loopholes in our gun laws that could prevent them remain.

On April 6, the father of one of the children who died at Columbine was in Maine to testify before a legislative committee in support of a bill that would close a loophole that allows people to purchase guns from private sellers at gun shows without a background check.

At the hearing, the father recalled how his son, just days before the shooting, had asked him at the dinner table whether he knew there were loopholes in the Brady bill, after learning of them in a high school debate class. The Brady bill required purchasers to wait up to five days for a background check to occur before being allowed to purchase a handgun.

It is a strange and sad coincidence that two weeks later, Tom Mauser’s son would die because of one of those loopholes. The guns used at Columbine were obtained through the same loophole that still exists in Maine. The bill Mauser is backing in Maine is similar to one he helped get passed in Colorado in 2000.

Opponents of the bill, which include the NRA and the Sportsman’s Alliance of Maine, argue that there is no loophole in the law, because licensed dealers are already required to do background checks under federal laws. They say private sellers at gun shows are rare.

If private sellers are rare, then it wouldn’t be too onerous to require them to do the same background checks required of other gun dealers. Most background checks take a minute and help prevent criminals and mentally ill people from obtaining guns. The checks aren’t going to stop sportsmen from obtaining guns legally for recreational uses, and they don’t violate the Second Amendment.

The arguments made by gun-rights groups are unconvincing, and particularly when made against the backdrop of so much violence. This is a loophole that should have been closed a decade ago, and the fact that it remains is unconscionable.

It needs to be closed before Maine becomes the next state to make the national news because of a violent rampage.

Brendan Moran, editor