Two weeks after two US border patrol agents were found with head injuries by a drainage channel next to a freeway in remote west Texas, how one of them died remains a mystery.

At least, the late-night incident in which 36-year-old Rogelio Martinez died is a puzzle to the FBI, which is investigating.

To Donald Trump and two prominent Texas Republicans, Governor Greg Abbott and US senator Ted Cruz, the cause of death was immediately clear: murder.

“Border Patrol Officer killed at Southern Border, another badly hurt,” Trump tweeted on 19 November, the day after the agents were hurt. “We will seek out and bring to justice those responsible. We will, and must, build the Wall!”

In remarks the following day, Trump described the surviving officer as having been “brutally beaten”.

Abbott authorised a $20,000 reward for information leading to the arrest and conviction of those responsible for the “murder”.

On 19 November, within a few hours of US Customs and Border Protection (CBP) announcing that Martinez had died in hospital after “responding to activity while on patrol”, Cruz issued a statement in which he said the agents had been “attacked”.

The senator also said the incident was “a stark reminder of the ongoing threat that an unsecure border poses to the safety of our communities and those charged with defending them”.

It did not escape the notice of some of Cruz’s online critics that earlier in November he visited Sutherland Springs, the day after 25 churchgoers were shot dead there. The senator told a reporter asking about gun control that “it is an unfortunate thing that the immediate place the media goes after any tragedy, after any murder, is politicizing it”.

Spokespeople for Cruz and Abbott did not immediately respond when asked how they determined that Martinez was murdered and whether this was still what they thought.

Border patrol pallbearers carry agent Rogelio Martinez to a graveside service at Restlawn Cemetery on 25 November in El Paso, Texas. Photograph: Mark Lambie/AP

Border Patrol union representatives have told reporters they are convinced it was foul play and that the agents were most likely attacked with rocks.

But Oscar Carrillo, the Culberson county sheriff who is based in Van Horn, a small town about 120 miles south-east of El Paso and about 30 miles from the border as the crow flies, and attended the scene, told the Dallas Morning News the officers might have been sideswiped by a large truck as they stood on the edge of a windswept road where drivers are liable to lose concentration and wander across lanes.

“From the beginning we were radioed to assist in the incident as an injury, not an assault,” he said. “That’s the way it was communicated to us.

“If this was an assault, believe me, as sheriff, I’d be the first one out there emphasizing safety in our community and with our deputies, pairing them up. But from what I know and see, that was not the case here.”

According to a CBP list, Martinez is the 40th border patrol officer to die in the line of duty since December 2003. That includes Trena McLaughlin, who died of liver failure in 2009 after contracting hepatitis C as a result of being “stuck with a syringe while searching a vehicle” in 1994. Of the other 38 fatalities, 32 resulted from accidents, heat-related illnesses or natural causes. In the 2016 fiscal year there were nearly 20,000 border patrol agents nationwide.

The FBI request for information about Rogelio Martinez. Photograph: AP

Distant from major population centres and featuring difficult terrain, the CBP’s Big Bend Sector, where Martinez died, is relatively quiet. It sees the fewest apprehensions along the south-west border: 1.6% of the total in the last fiscal year.

But the assertion of murder, presumably by Mexican drug or people smugglers, suited Trump’s narrative that the frontier is insecure and in need of a wall and that many immigrants already in the US represent a safety threat.

This week, Trump railed against the decision of a San Francisco jury to acquit an undocumented Mexican immigrant charged with the murder of Kate Steinle, whose death he cited during his presidential campaign.

Full autopsy results on Martinez’s body have not yet been released. The unnamed agent who survived was released from hospital but reportedly does not remember what happened.

The FBI has been cautious. It held a detail-light press conference on 21 November in which Emmerson Buie Jr, the special agent in charge of the agency’s El Paso division, termed the event a “potential assault”.



The possibility of an accident has not been ruled out. Could the men have fallen into the culvert below Interstate 10 near Van Horn, in a part of the state which has some of the darkest night skies in the country?

On Thursday, the FBI issued a statement regarding what it called a “tragic incident” and announcing a campaign to run on digital billboards in south-west border states from 30 November to 8 December, highlighting “an FBI reward of up to $45,000 for information leading to the resolution of the investigation into the death”.