An FBI official said Tuesday that the bureau is investigating the death of a border patrol agent and injuring of another as "potential assault," but he wouldn't rule out that they could have been injured in some other way.
During a news conference at the bureau's El Paso office, Special Agent in Charge Emmerson Buie Jr. said investigators are still trying to "gather the facts," but they are currently treating it as an assault on a federal officer.
Rogelio Martinez, a 36-year-old U.S. Customs and Border Protection agent from El Paso, died Sunday and his partner, whose name has not been released, was seriously injured. They were found late Saturday in a culvert near Van Horn, about 30 miles (50 kilometers) from the border with Mexico and 110 miles (175 kilometers).
An FBI spokeswoman, Jeanette Harper, said in a news release Monday that both agents had traumatic head injuries. The agent who survived was hospitalized in serious condition. She told the San Antonio Express-News on Sunday that the agents were "not fired upon," but she didn't elaborate.
A U.S. official with knowledge of the investigation told the Associated Press on Monday that Martinez was found at the bottom of the culvert and investigators believe he may have fallen. The official said Martinez's partner, who radioed for help, has no memory of what happened. The official, who was briefed on the investigation but is not authorized to speak publicly and spoke on condition of anonymity, said it happened after dark in an area that's known for drug activity and where agents often look for drugs in culverts.
At Tuesday's news conference, Buie and Border Patrol officials who spoke did not say why they believed the agents may have been attacked.
Rush Carter, a border patrol supervisor for the region that includes the area where the agents were hurt, said Monday night that reports it was an attack were "speculation." But several elected officials, including President Donald Trump, referred to it as such. When asked about the president's remarks Tuesday, Buie said he had not briefed Trump on the investigation.
Carter said all the agency could confirm is that the two "were injured while performing their regular duties."
"We are waiting for the investigation to fully determine how those injuries happened," Carter said Monday night.
Martinez's father told the El Paso Times that his son suffered serious injuries that left his head "destroyed." The agent repeatedly suffered cardiac arrest before succumbing to his injuries, an emotional Jose Martinez said.
"I would tell him, 'Son, that job is too dangerous.' But he would say, 'Dad, it's the job I like. I want to defend my country from terrorists. ... I want to prevent terrorists and drugs from coming into the country,'" Martinez said.
Martinez's mother, Elvia Martinez, told The Associated Press on Tuesday that she and her husband didn't yet know any details about the circumstances surrounding their son's death.
"He was a very accomplished person and loved his work," she said tearfully.
Rogelio Martinez, father to an 11-year-old, joined the Border Patrol in 2013.
Authorities have been slow to release information about the investigation.
Kevin McAleenan, acting commissioner of CBP, said in a letter sent to border agents on Sunday that Martinez was unconscious when agents found him with "multiple injuries" to his head and body.
Chris Cabrera, a spokesman for a border patrol agents union, the National Border Patrol Council, told The Associated Press that the two agents appeared to have been struck in the head with a rock or rocks. Cabrera said agents who responded to the scene described it as "grisly" and said Martinez and his partner had "extensive injuries."
Texas Gov. Greg Abbott announced a $20,000 reward Monday for information that leads to an arrest or conviction in the case. The Republican also tweeted that "resources must be increased to prevent these attacks in the future." The FBI added a reward of up to $25,000 for information that leads to a resolution in the case Tuesday.
Republican Sen. Ted Cruz took a similar approach in a news release: "We are grateful for the courage and sacrifice of our border agents who have dedicated their lives to keeping us safe."
Trump took to Twitter on Sunday to insist that Martinez's death underscores the need for a wall along the border between the U.S. and Mexico.
"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!" he tweeted.
The president offered his condolences to Martinez's family. He also said Martinez's partner was "brutally beaten and badly, badly hurt" but that it "looks like he'll make it."
Authorities haven't said whether they have any suspects or whether they think smugglers or people who were in the country illegally were involved.
Border Patrol records show that the agency's Big Bend sector, which includes the area where the incident occurred, accounted for about 1 percent of the more than 61,000 apprehensions its agents made along the Southwest border between October 2016 and May 2017. The region's mountains make it a difficult area for people to cross illegally into the U.S. from Mexico.
The Border Patrol website lists 38 agents, not including Martinez, who have died since late 2003. Some were attacked while working along the border and others were killed in traffic accidents.
Martinez is the second agent to have died this year.
Associated Press writers Emily Schmall in Fort Worth and Elliot Spagat in San Diego contributed to this report.