Washington — Fifty days after U.S. officials vowed to conduct a "swift"who aggressively confronted migrants in Del Rio, Texas, the probe remains ongoing, frustrating both the labor union representing the officers and immigration advocates pushing for more accountability.
Images of mounted agents dispersing migrants along the Rio Grande prompted nationwide outrage in September, as more than 15,000 migrants — including thousands of Haitian asylum-seekers — amassed in a makeshift camp under the Del Rio international bridge.
"This is why your country's s**t, because you use your women for this," one mounted agent was heard on video telling a migrant man huddled with a group of women and children.
Days after the confrontation, Mayorkas announced Border Patrol agents at the center of the investigation were placed on administrative duty and banned from interacting with migrants.
"I want to assure you that we are addressing this with tremendous speed and tremendous force," Homeland Security Secretary Alejandro Mayorkas vowed in late September, adding that the investigation by the Department of Homeland Security (DHS) Office of Professional Responsibility would "be completed in days — not weeks." President Biden called the incident "outrageous," and said, "I promise you, those people will pay."
At least six border agents were slated to sit down with DHS investigators to offer their own accounts of what happened in interviews on Tuesday and Wednesday, according to law enforcement officials granted anonymity because they were not authorized to speak about the pending investigation. At least one of the agents at the center of the probe — the officer seen wielding a rope known as a lariat while grabbing a migrant by the collar — has not yet been contacted for an interview.
The head of the National Border Patrol Council (NBPC), the Border Patrol's largest union, expressed frustration that the investigation has dragged on for weeks. The union is providing legal representation for the officers involved in the probe.
"I'm very disappointed that this investigation has taken as long as it has taken," said Brandon Judd, president of the NBPC. "I believe that the reason it has taken so long is because of what we've heard from some of the most powerful people in the world."
Two former leaders from Customs and Border Protection (CBP), which oversees the Border Patrol, offered differing assessments of the incident, with one questioning the use of the mounted officers in the first place and another saying the officers did not violate any internal policy and should be cleared of wrongdoing.
"I think the disappointing part from what I saw is when agents went out into an open area," Gil Kerlikowske, a former CBP commissioner during the Obama administration, told CBS News.
"There are agricultural areas along the side of the interstate where horse mounted units could certainly be useful in responding to those who are injured or hiding," Kerlikowske said. "But when they came out into the open area, with families crossing, I did not think that was a sound, tactical decision."
Kerlikowske, who oversaw the establishment of CBP's first office of internal affairs, added that agency leaders should also be held accountable.
"Did agents go out on their own? Were they dispatched or directed there? Were they told to stay back in the underbrush? Those questions have to be answered because it will be unfair if you only hold the agents on horseback accountable," he said.
The examination of alleged misconduct by Border Patrol agents is the latest in a series of CBPand comes as the Biden administration struggles to address historic numbers of migrant crossings at the U.S.-Mexico border. The administration initially vowed to demobilize units of Border Patrol agents on horseback in Del Rio during its investigation, but mounted units have since resumed operations.
"I don't think there's a state in the union that doesn't have a horse patrol," former Border Patrol Chief Rodney Scott said. Scott, who departed the agency in August, noted that customs officers have been riding horses for decades, and the units are deployed in treacherous terrain where "you certainly can't take an ATV or truck."
"If they're looking at policies, I can tell you that Border Patrol agents didn't violate any actual policy," Scott said. "There's no reason that this shouldn't be open and shut already."
And while immigration advocates share the frustration in the slow pace of the investigation, they have also called on DHS to establish more oversight of cavalry units. The American Civil Liberties Union (ACLU) of Texas wrote a letter to Mayorkas in late September urging CBP to update its "use of force" policy to "appropriately limit the use of horse-mounted agents, lariats, and abusive language."
"It certainly should not have taken five days, let alone 50 days to conduct an investigation into activities that are so blatantly and clearly caught on camera," said Shaw Drake, staff attorney and policy counsel for the American Civil Liberties Union of Texas. "This incident in Del Rio is an isolated event that exposes specific issues with horse mounted units and CBP 'Use of Force' policy, but it's also a symptom of a larger problem."
In the weeks since confrontation between the mounted agents and migrants, the U.S. government has carried out 80 deportation flights to Haiti, expelling 8,497 people, 44% of whom are women and children, according to the latest International Organization for Migration (IOM) data.
The Department of Homeland Security did not respond to CBS News' request for comment on the investigation into the mounted officers.
Camilo Montoya-Galvez contributed to this report.
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