Thousands of Haitian migrants have appeared at the US-Mexico border seeking to cross the Rio Grande and find refuge in the US. Human rights activists are condemning images of US border agents, mounted on horseback, trying to head off migrants almost as if they’re herding cattle. The US special envoy to Haiti, Daniel Foote, has now resigned to protest the Biden administration’s “inhumane” effort to send them back to Haiti. At the same time, conservative lawmakers are accusing the Biden administration of failing to head off another crisis at the border and the distressing images of the massive migrant camp in Del Rio, Texas, back up that idea. How Haitian migrants, would-be refugees fleeing an island nation that is rocked by political instability and economic depression, converged at once at the US-Mexico border in a specific spot in Texas is complicated. So is the question of will happen to them next. Read the latest report from CNN’s Priscilla Alvarez and Rosa Flores. What’s happening now: How big is this surge? The numbers are incredible; the number of migrants swelled from about 400 to a max of 14,000 in days. More could be on the way according to CNN’s Alvarez, who writes: There are up to 30,000 Haitians in Colombia who may be seeking to travel north, CNN has learned. The department is tracking between 40,000 to 60,000 Haitians in the hemisphere, though they are not necessarily seeking to come to the US, according to the congressional aide. Recently, Mexico also stopped some buses of Haitians coming north, DHS said, according to the aide. Why are Haitians, specifically, coming to the US border? Back in May, Mayorkas announced an 18-month temporary protective status for Haitians already residing in the US, which now applies to Haitians in the country as of July 29. Mayorkas had cited “security concerns, social unrest, an increase in human rights abuses, crippling poverty, and lack of basic resources, which are exacerbated by the Covid-19 pandemic.” And that spring announcement was before Haiti’s president was assassinated and an earthquake struck over the summer. Many of those arriving at the US border now had left Haiti long ago and were either living or staying in other Central and South American countries, from Guatemala to Chile. CNN talked to 26-year-old Jameson Tilus. He fled Haiti years ago after he was assaulted in his home and his aunt was shot at. In Chile since 2015, he wants to join his brother, uncle and cousins, who are in the US. Friends told his family the border was open in Del Rio, so Tilus, his wife, their 5 year-old daughter and their 3 year-old son started the two-month journey there. “I’m 26 years old, and I don’t have a profession,” Tilus said, his voice breaking. “I was doing very badly, I wanted a better life.” Read more. What’s the US plan? Here’s what Mayorkas told lawmakers after visiting the border Monday: “The plan that we have is a multi-part plan. What are the critics saying? Patrice Lawrence leads the group UndocuBlack, which advocates for undocumented Black people in the US. She writes for CNN that the Biden administration should be distinguishing itself from the Trump administration and allowing for a more orderly asylum process rather than flying Haitians back to Haiti. “The Biden administration could have made a strong statement in favor of due process and dignity by allowing for an orderly asylum process. Instead, it has opted for mass expulsions of vulnerable people.” On the other side of the spectrum is Texas Republican Gov. Greg Abbott and his wall of police cars. “When you have an administration that is not enforcing the law in this country, when you have an administration that has abandoned any pretense of securing the border and securing our sovereignty, you see the onrush of people like what we saw walking across this dam that is right behind me,” Abbott said at a news conference in Val Verde County. This story has been updated to reflect the latest developments.