The first sign that the Sandy Hook Elementary School massacre has changed the way we talk about guns in this country came from an unlikely place — Wall Street.

Cerebrus Capital Management, a private equity firm and hedge fund, announced that it would immediately divest its ownership of the Freedom Group, a conglomeration of gun manufacturers including the maker of the Bushmaster rifle believed to be used to gun down 20 first-graders and six adults last week.

The decision came because the California teachers pension fund, which is one of Cerebrus’ biggest investor groups, said it would re-evaluate its involvement in the fund in light of the mass killings in Connecticut. It said retirees should not be making money on weapons that kill innocent children, especially when the sale of guns such as the one used in Newtown are illegal in California.

The decision has a lot more significance than the effect such a sale would have on Cerebrus’ balance sheet.

The National Rifle Association has dominated the gun control debate in recent years, offering an absolute position against any new gun control measure — no matter how reasonable — claiming that it would create a slippery slope to gun confiscation.

This has been a very successful strategy, even after previous mass killings. But the sights and sounds from Newtown may have changed people’s minds.

People who were not strong proponents of gun ownership rights or gun control have been awakened to the pain and anguish that can be unleashed by a deranged person who is armed. A shift in attitude by the people in the vital middle, such as the retirees in California, could change the terms of this debate.

Mass killings attract attention, but gun violence is a daily event in this country and families mourn every day, the same way the families in Newtown are mourning. Now that so many Americans have been touched by Newtown, their attitude toward gun violence in general may be changing.

We have learned from tragedies before. Our airplanes are safer since 9/11. We can learn from Newtown, too.

The pension fund’s decision may be a sign that this is already happening.