These deadly racist attacks should be impossible, but they're becoming more common

A young white man wielding a weapon marked with a swastika. A trail of manifestos espousing far-right ideologies. Victims killed because of their race.

It's a situation that should be impossible, or at least uncommon.

"We have three people who are dead because they are Black," Democratic Florida state Sen. Tracie Davis said at a vigil in Jacksonville, Fla., this week after the gruesome attack at a Dollar General store. "Shopping. In our community. Gunned down. Because they were Black."

But the shots fired by a 21-year-old — leaving families grieving and a community at loss over yet another act of gun violence — are no longer so unusual in America, say experts who study gun violence and racist extremism.

In fact, data show that racist shootings are becoming more common.

In a report tallied extremist mass killings and attempted ones, finding that 46 took place since the 1970s. Each was at the hands of extremists motivated by far-right, far-left or radical Islamist ideology, with a small number connected to lesser known extremist ideas. But since 2011, it's been right-wing extremists behind the majority of attacks. Most of those were carried out by white supremacists.