When reports of a mass shooting reached officials in Washington, D.C., the U.S. Senate buildings were among those locked down. Let's hope the irony wasn't lost on their occupants.

Another mass shooting. More people suffering. At this writing we know that at least 13 people were killed and more wounded after a shooter (or multiple shooters) opened fire at the historic Washington Navy Yard on Monday.

Details are still sketchy, but The Washington Post reported that the FBI identified one of the deceased, Aaron Alexis, 34, of Fort Worth, Texas, as the suspected shooter, although police were uncertain if he acted alone. Early reports said Mr. Alexis was a former naval reservist and a military contractor. Sources told the Post he had an assault rifle and a pistol, and possibly other guns.

Where might he have gotten them? Might he have been stopped by a background check?

Just five months ago, a mile and a half away at the U.S. Capitol, the U.S. Senate defeated a compromise proposal to expand background checks on gun purchases, despite vast public support for the proposal.

The gun control proposals had followed the horrific massacre at Sandy Hook Elementary School in Newtown in December, where a deranged gunman killed 20 children and six educators before taking his own life. The Senate proposal would have required background checks for sales at gun shows and the Internet, closing glaring loopholes in current law.

Is there a place in America that hasn't been touched by a mass shooting? Has it become part of life in this country? About 3,000 people, military and civilian, work in the building where the shooting took place. We ask for senators who voted against the gun control bill to go down there tomorrow and look them in the eye.