Gun and ammo stocks tend to rise after the most widely-covered mass shootings. Today was no exception. Shares of top gun and ammunition companies soared the morning after a school shooting in Uvalde, Texas that left at least 20 people dead.

Investors anticipate that the violence—and the political rhetoric about gun control that inevitably follows—will prompt more people to buy guns and stock up on ammunition. It’s true gun sales typically rise after a mass shooting as more people arm themselves, ostensibly, to defend themselves against future shooters (although there’s no clear evidence that using a gun in self-defense reduces the likelihood of being injured in an attack). Others rush to buy guns in the belief that lawmakers will soon enact stricter restrictions on gun sales.