Federal investigators are treating a shooting on Saturday at a Walmart in El Paso, Tex., as an act of domestic terrorism. At least 20 people were killed and 26 wounded. Less than 24 hours later, a gunman opened fire in Dayton, Ohio, killing at least nine people and wounding 27 others.

The back-to-back attacks bring the number of mass shootings in the U.S. this year to 32.

White male suspects: In El Paso, a 21-year-old Texan named Patrick Crusius surrendered to the police, and the authorities were investigating a hate-filled, anti-immigrant manifesto that he may have posted online minutes before the attack detailing “the Hispanic invasion of Texas.”

In Dayton, a heavily armed gunman wearing body armor, identified as a 24-year-old resident named Connor Betts, was shot dead by the police.

Go deeper: The number of attacks by white extremists in the global West is growing, and at least a third of the killers since 2011 drew inspiration from other perpetrators, according to a Times analysis. An international comparison shows that the high rate of mass shootings in the U.S. stems from the country’s astronomical number of guns.

8chan: The online messaging board where the manifesto was posted before the El Paso attack has become a megaphone for mass shooters and a recruiting platform for white nationalists. Its founder wants to “shut the site down.”