Oscar Carrillo made an unusual choice for a kid who grew up in mid-eighties El Paso: he chose to become a small-town West Texas lawman. “I could very easily have chosen to work in a large city, make the higher salary, enjoy the scheduled days off and paid vacations, and benefit from the almighty overtime pay,” Carrillo said. “But smaller, rural, remote, and not-so-wealthy jurisdictions deserve competent, experienced, and well-trained law enforcement too.”

The 52-year-old first served as a sheriff’s deputy in Howard and Midland counties before he became Marfa’s police chief. Since 2000, he has been the sheriff of Culberson County, a large, desolate swath of hardscrabble land wedged between New Mexico and Mexico in the state’s far western tip. Culberson County sprawls over 3,800 square miles, larger than Delaware and Rhode Island combined. Ranchland bumps up against Blue Origin, Jeff Bezos’s private spaceport project. There are no police departments, just the sheriff and his deputies.

You wouldn’t have any trouble identifying Carrillo as the sheriff if you bumped into him on the streets of Van Horn, the county seat and home to nearly all its 2,200 residents: he’s usually decked out in a white cowboy hat, work shirt with a tie, blue jeans, sidearm on his hip, and a star on his chest. Like many cops, Carrillo has a well-defined sense of right and wrong, and he’s not shy about voicing it, even if that means contradicting the governor of Texas or the president of the United States.

The weekend before Thanksgiving 2017, that’s exactly what happened, as Van Horn became the center of a border security debate.

Late on Saturday, November 18, Border Patrol agents Rogelio Martinez, 36, and Stephen Garland, 38, sustained serious injuries at the bottom of a culvert along a remote stretch of Interstate 10, about twelve miles east of Van Horn. Martinez died later in an El Paso hospital from blunt injuries to the head, according to the El Paso medical examiner. But the manner of his death remains undetermined and has become the subject of often venomous debate.

Garland survived but has no memory of the night’s events, officials have said.

Carrillo was among the first responders at the scene. He doesn’t recall ever meeting Martinez or Garland, though he later learned that he and Martinez had both graduated from El Paso’s Irvin High School, sixteen years apart. But as a fellow law enforcement officer, Carrillo felt the tragedy deeply.

His mourning turned to anger, however, as word quickly spread about the incident. Martinez’s colleagues and prominent Republicans jumped to the conclusion that he had been the victim of a homicide, describing the scene in a way that bore no resemblance to what Carrillo had witnessed and what decades of experience told him had likely happened.

“Border Patrol Officer killed at Southern Border, another badly hurt. We will seek out and bring to justice those responsible. We will, and must, build the Wall!” President Trump tweeted the day Martinez died.

“I’m offering a reward to help solve this murder of a Border Patrol Agent in Texas. Help us catch this killer,” Governor Greg Abbott tweeted on November 20, offering up to $20,000. The elected officials were describing a version of events that mirrored what the National Border Patrol Council, the agents’ politically powerful union, had offered. “What we know is that Border Patrol Agent Rogelio Martinez appears to have been ambushed by a group of illegal aliens whom he was tracking. Our agents’ reports from the ground say that he was struck in the head multiple times with a rock or rocks,” NBPC president Brandon Judd told Breitbart Texas on November 19, shortly after Martinez’s death. Other media jumped on the attack story. The rush to judgment was on.

To the sheriff, Martinez’s injuries looked consistent with a fall, not a beating, because they were limited to one side of his body instead of all over. He said medical staff who saw Martinez told him the same thing. Yet it was difficult to get that information out to the public.

Carrillo was witnessing a political phenomenon familiar to anyone who has paid attention to the immigration debate: opinions quickly trample facts, and facts often aren’t welcome when they interfere with a good narrative.

I arrived in Van Horn the day after Martinez died to report on the story for the Washington Post. I didn’t bump into any other reporters that day. A Fox News reporter would later visit with Judd; otherwise, the national media was visibly absent from the isolated scene.

Van Horn sits about 120 miles southeast of El Paso. Contrary to Trump’s tweet, it is not located “at [the] Southern border”; it’s 30 miles from the boundary as the crow flies, and the nearest international crossing is 70 miles away. The Border Patrol’s Van Horn station sits on Interstate 10, which is the biggest east-west artery near the Mexican border.

A 26-year law enforcement veteran, Carrillo has experience batting down questionable or false information about the border. In 2014, a group calling itself the Border Convoy issued a “media alert” saying its members had been evacuated from the Comfort Inn in Van Horn to save them from drug cartel forces spotted nearby. There hasn’t been a Comfort Inn in Van Horn since 2006, and there was no evacuation of any motel. “It’s all false,” Carrillo said at the time.

And now Carrillo found himself again responding to descriptions of events he didn’t recognize. He said numerous questions needed to be answered to understand what happened to Martinez and Garland. “Why is the other guy [Garland] hurt? That is the game changer. That’s the unknown. What happened to him? Or did they both fall? We don’t know,” he said. The Washington Post published Carrillo’s comments, which contradicted Abbott’s and Trump’s versions of events, and they were picked up by other media.

The FBI opened an investigation into the federal agent’s death. It held a press conference in El Paso on November 21 in which it labeled the incident a “potential assault of a federal officer” but cautioned that investigators hadn’t reached any conclusions as to what had happened. The rush to judgment suddenly slowed.

Officials from the Border Patrol union, which had endorsed Trump in the 2016 presidential campaign and supported his call for increased border security, mocked Carrillo for claiming the agents might have fallen. “Border Patrol agents are like mountain goats when it comes to terrain. We don’t fall,” a union spokesman, Chris Cabrera, said on his podcast, The Greenline, on November 29. “For somebody to say we fell off a highway culvert, you’re out of your mind. That doesn’t happen.” Later in the podcast, Cabrera told union vice president and co-host Art Del Cueto, “It disgusts me that not only did this happen, but that somebody, somewhere along the line, is backtracking and saying, ‘Oh, he fell, he fell.’ You know what, screw you. He did not fall.”

Cabrera referred to Carrillo as “that dingbat sheriff” in his next podcast, on December 11. “I question this sheriff—I don’t know his name, but the sheriff out there in Van Horn. I question his motives for saying it was an accident, because that can’t do anything but hurt the prosecution’s case when they get somebody in custody. He doesn’t seem like he’s too bright of a guy there,” said Cabrera, who is based in the Border Patrol’s Rio Grande Valley Sector.

The attack from the union, amplified by social media, quickly reached Carrillo, who is used to stereotypes of small-town cops as bumbling, Barney Fife types. “The criticism came from everywhere. I even shut down my office’s web page, which was loaded with negative comments from mid-America.” The criticisms continued to mount until February 7, when the FBI issued a news release on its investigation that largely aligned with what Carrillo had been saying from the beginning. “To date none of the more than 650 interviews completed, locations searched, or evidence collected and analyzed have produced evidence that would support the existence of a scuffle, altercation, or attack,” the release stated. According to the FBI, a dispatcher who spoke to Garland as he called for help said he told her, “We ran into a culvert,” “I ran into a culvert,” or “I think I ran into a culvert.” In an email sent shortly after the FBI released its statement, then-acting Customs and Border Protection commissioner Kevin McAleenan said evidence indicated that the agents had fallen into a culvert adjacent to the highway about 22 feet from each other.

“The absence of evidence is a key factor in this case—not due to lack of effort or determination, but because evidence which would indicate the presence of other persons or the commission of a criminal act is not present,” McAleenan wrote. “As an example, there were no defensive wounds on Agent Martinez or his partner who suffered injuries in this incident, and there was no third-party blood or DNA evidence recovered from the scene or from the agents’ clothing.”

The El Paso County medical examiner listed the manner of Martinez’s death as undetermined, but forensic pathologists who reviewed the autopsy report for the Washington Post and CBS News said his injuries were more consistent with a fall than an assault. The FBI said Martinez and Garland had been “conducting routine checks of culverts in the area” on the night of November 18, as smugglers and immigrants regularly use those culverts as thoroughfares. Carrillo said their patrol vehicles were parked on the south side of I-10, but they were injured on the north side of the freeway, at the bottom of an eight-and-a-half-foot concrete culvert that ran beneath the freeway. He believes it is likely the agents were running across the highway to check a culvert and lost their bearings on that moonless night.

After exiting their vehicles, the agents would have crossed two eastbound lanes, a median, and two westbound lanes before coming to a 9-foot-wide shoulder. They then had to cross a 21-foot grassy hill that sloped down from the shoulder before dropping off abruptly to the desert floor beneath the culvert structure.

“It is very possible the agents crossed the center median onto the north side of the interstate and did not see the drop,” Carrillo said. “The edge of the culvert has no railing and isn’t marked in any way for someone approaching it from the south. The area can be difficult to navigate in the dark.”

In early April, Trump renewed and amplified his rhetoric on border security, authorizing the National Guard to deploy troops to the border. Trump and Abbott have not spoken about the Van Horn incident since the FBI report was issued, and Abbott has declined to respond to multiple media inquiries. The Border Patrol union continues to insist Martinez and Garland were attacked. “Just because there’s no evidence of a scuffle doesn’t mean that it wasn’t an assault,” Judd told Fox News.

Carrillo says the Border Patrol union and others are driven by a political agenda. “On a sad note, the union decided early to exploit a Border Patrol agent’s death for their political purposes, and they were not alone. I felt the incident pushed a distorted portrayal of immigrants and the border as a way to advocate border insecurity.”

To underscore that point, Carrillo said that, in March, his deputies were sent to another culvert on Interstate 10, about five miles from where Martinez was fatally wounded. “On Friday the 9th, a 25-year-old female was flown to El Paso with head injuries sustained from falling into a culvert off Interstate 10 as she fled from Border Patrol agents east of Van Horn,” Carrillo told me in a text message. Border Patrol officials said the woman survived her injuries. “So it does happen. But no one seems to be interested.”

Robert Moore is a former executive editor of the El Paso Times.