What's the correlation between school shooting deaths and defensive gun uses?

Between 1998 and 2015, some 344 mass shootings were reported across the states, according to data from the Uniform Crime Reports, with 263 of those incidents nondomestic and 81 domestic. Since 2010, more mass shootings have been carried out in states with lax gun laws, while the opposite trend emerged in states with stricter laws. A 10 percent rise in gun ownership was linked to a 35 percent higher rate of mass shootings. In 2018, there were 2x as many children killed by guns in states with more lenient gun laws than those with strict laws.

... perhaps you're suggesting that those people who own guns for defence are just not defending those people being killed by gunmen? That defensive gun uses are down because people don't use guns to defend?

If that's the case, what's the point in owning a gun for defence if you're not using it to defend those that need defence?