A US Border Patrol agent working at a processing center in El Paso, Texas, was indicted last week on multiple federal charges, including bribery and "alien smuggling," after he allegedly offered a migrant an "immigration benefit" in exchange for $5,000, according to court documents.
The charges against the agent, Fernando Castillo, come about a month after his arrest as investigators gathered a trove of evidence thanks to the cooperation of the migrant.
In a probable cause affidavit supporting Castillo's arrest warrant, the unnamed migrant is identified as a victim who is Mexican and El Salvadoran and has no criminal history. It says the migrant had encountered US immigration authorities twice but no charges were filed.
An investigation was launched after the migrant notified border patrol agents of Castillo's alleged actions, the affidavit says.
The migrant, who was scheduled to be returned to Mexico on June 21, told investigators Castillo volunteered to drive them to a port of entry in El Paso for the repatriation, according to the affidavit.
Castillo allegedly made a stop along the way and told the migrant he could get them "papeles," or immigration papers, for $5,000, the affidavit says. The agent said that once the migrant was in the US, the "papers" would "no longer appear in any system" after a couple of days and the migrant could "essentially be free to remain in the US," according to the affidavit.
The migrant told investigators that during the stop, Castillo opened their heat-sealed personal property bag and reached inside, the affidavit shows. The migrant said the agent then brought them to a second processing center, where Castillo placed them in a holding cell and resealed the property bag, according to the document.
Surveillance video at the second processing center showed a uniformed border patrol agent fitting Castillo's physical description escorting the migrant into the facility, according to the affidavit.
Soon thereafter, Castillo escorted the migrant to an El Paso port of entry for the scheduled voluntary return to Mexico, according to the affidavit.
Once in Mexico, the migrant said they opened their property bag to purchase shoelaces and discovered that $500 "had been stolen," according to the affidavit. After discovering this, the migrant returned to the port of entry and notified border patrol agents, which launched an investigation, it says.
When investigators later examined the property bag, they found it contained $330 and 3,700 Mexican pesos, but the tag on the bag said it contained $830 and 3,725 Mexican pesos, the criminal complaint says.
Investigating agencies included the FBI, the US Customs and Border Protection's Public Corruption Task Force and the Department of Homeland Security Office of the Inspector General.
Investigation reveals call records and the agent's meetup with migrant
Following the incident, the migrant received several calls from a "blocked number" that investigators believe was Castillo, the affidavit says. Investigators also recorded calls which came in while they were interviewing the migrant, in which a caller believed to be Castillo discussed how the migrant would receive the immigration papers, when he would escort them back into the US and when the money would be exchanged, the affidavit states.
Castillo was charged with wire fraud in connection with the alleged calls, according to the indictment.
Investigators also ran an audit of the migrant's immigration file -- which tracks all agent generated actions in the system -- and discovered Castillo had modified the migrant's file from a "Voluntary Return" to Mexico to "Notice to Appear," meaning the migrant would have a "legal reason to enter the United States," the affidavit states.
On June 28, federal agents watched Castillo as he left his home and met the migrant at an El Paso port of entry, the probable cause affidavit states. With the "Notice to Appear" form in hand, he took the migrant through the "voluntary removal area" and exited through a "fenced in" area, the document states.
The $5,000 was not exchanged, according to the probable cause affidavit, because Castillo allegedly told the migrant to hold on to the money until they got to the vehicle.
During his interview with federal investigators, Castillo denied taking the migrant's $500, but admitted to changing their file, forging signatures of border patrol agents and carrying the false document to meet up with the victim, per the affidavit.
CNN has reached out to Randolph Ortega, Castillo's attorney, and has yet to hear back. The US Attorney's Office of the Western District of Texas declined to comment.
Castillo's service with US Customs and Border Protection ended on July 13, according to a source familiar with the investigation. The agency says it's cooperating with the investigation.
"CBP takes allegations of misconduct seriously and investigates them thoroughly," the agency said in a statement.
Castillo's bond was set at $30,000 and he was released from jail on June 29, El Paso jail records show. His arraignment is set for August 17 in an El Paso federal courtroom, according to the court docket.