The United States Flag Code only allows for the flag to be flown at half-staff for a certain number of reasons. Recently, protocol was broken to respect the five military victims of the recent terrorist attack in Chattanooga.
However, it seems like the flag should be flown at half-staff whenever there is a mass shooting. We all love our country and anytime there is such violence it is a loss for the country. It would also raise the issue of the sheer number of mass shootings we have in this country....effectively one a day.
Since legislation is not likely to happen, it seems the debate should at least be commenced.