He was a young gunman bent on shooting as many worshippers as possible, but Matthew J. Murray never got as far as Dylann Roof, the suspect in Wednesday's South Carolina church massacre.

Murray had already shot and killed two people in the parking lot when he burst into the New Life Church in Colorado Springs. Before he could pull the trigger again, however, the 24-year-old shooter was gunned down by Jeanne Assam, a volunteer security guard with a concealed-carry permit.

That was eight years ago, but even though Ms. Assam was credited for saving as many as 100 lives that day, a dozen states continue to restrict the carrying of concealed firearms in churches — including South Carolina.

The Emanuel AME Church shooting that left nine dead Wednesday prompted not just a surge in calls from the left for tighter gun-control laws, but also pleas from the right for churches to protect themselves by allowing their parishioners to pack heat.