Last year , as part of an effort to carry out President Trump’s promise of “extreme vetting” of visitors to the United States, the Department of Homeland Security began collecting social media account information from millions of people seeking to cross the border.

After all, a radical online could be a radical offline.

That’s why the stream of posts ricocheting around a 9,500-member Facebook group, comprising current and former Border Patrol agent s as well as some people with no apparent connection to the Border Patrol, is so troubling. Members of the group, as documented by ProPublica this week, “joked about the deaths of migrants, discussed throwing burritos at Latino members of Congress visiting a detention facility in Texas on Monday and posted a vulgar illustration depicting Rep. Alexandria Ocasio-Cortez engaged in oral sex with a detained migrant, according to screenshots of their postings.”

Of a 16-year-old migrant from Guatemala who died while in Border Patrol custody in May, a member of the group wrote, “If he dies, he dies.”

Customs and Border Protection said on Monday that it had informed the Department of Homeland Security’s inspector general about the posts and had started its own investigation. The National Border Patrol union decried the posts as “inappropriate and unprofessional.”