Newtown, Columbine, Aurora, Colo., Fort Hood, Virginia Tech, Charleston ... all trigger visions of gun-massacre carnage, now erupting so much more frequently that the aftermath typically follows a depressingly predictable script.

Amid post-mortem mourning and hand-wringing, reasonable people repeat the same question asked after every such spree: What can we do to keep deranged criminals from possessing guns?

The answer, shamefully, always seems to be: Not much.

The latest example of such apparent futility stems from letters that 13 U.S. senators sent to three gun retailers in the wake of the June shooting deaths of nine members of a historically black church in Charleston, S.C., allegedly by a 21-year-old high school dropout with a police record who posted racist rants on his website.

The suspect, Dylann Roof, allegedly took advantage of a loophole in the law and was allowed to buy a .45-caliber handgun police say was used in the shootings before completion of a background check that would have prevented the sale.

The letters, asking the dealers – Missouri-based Bass Pro Shops, Nebraska’s Cabela’s and EZPawn of Texas – to change their policies so that “your products do not get into the hands of dangerous individuals,” has failed to evoke any response.

Last week, Connecticut’s two senators, Richard Blumenthal and Chris Murphy, who both signed the letter, called for a consumer boycott of the companies, which own retail outlets here and throughout the country.

Though well-intentioned, we believe such pressure does not carry much clout.

The best solution, as this newspaper has repeatedly advocated, is passage of legislation all responsible Americans – gun owners as well as the unarmed alike – should support. To their credit, Sens. Blumenthal and Murphy both have been strong proponents of more stringent gun laws, but so-called Red State representatives who fear incurring the wrath of the gun lobby have resisted.

We understand the power of the National Rifle Association and other gun rights groups, but note that Congress has been able to pass unrelated landmark legislation despite considerably less-than-unanimous support.

Consider the Affordable Care Act – few laws encountered more furious opposition, yet the Obama administration eventually prevailed, much for the common good.

The president and congressional leaders must similarly make passage of common-sense gun laws a top priority.

The loophole that needs closing seems like an easy enough fix. Federal law now requires firearms dealers to conduct background checks on would-be buyers. In nearly all cases dealers quickly complete these checks, but if questions arise the FBI or Bureau of Alcohol, Tobacco, Firearms and Explosives take a closer look. However, a provision of the Brady Handgun Violence Act allows retailers to sell a weapon after three days if federal authorities haven’t finished their check. The checks are intended to block firearm sales to anyone who has spent a year of more in prison, has been convicted of domestic violence or who is the subject of a restraining order, is a fugitive from justice, is a drug addict, has been committed to a mental institution, is a foreigner without proper documentation or has been dishonorably discharged from the military.

The proposed legilsation would force dealers to hold off on sales while applications are pending.

This makes perfectly good sense, and would help reverse a troubling trend in this country.

Since 1982, 572 people have been killed and 522 injured in mass shootings, and these horrific incidents now take place on average every three months or so, up from fewer than two times a year.

We cannot allow escalation to continue, just as we cannot allow ourselves to keep asking the same question: What can we do?

One answer is simple and straightforward. Close the loophole, thus keeping weapons away from those who have forfeited the right to own them.