On Saturday, agents arrested 34-year-old Abigael Calvo-Calvo after he illegally crossed the border near Naco.
Federal Bureau of Investigation officials say they are investigating the death of a border patrol agent and injuring of another in West Texas as a "potential assault", but they wouldn't rule out that they were injured in some other way.
During a press conference on Tuesday, the FBI Special Agent-in-Charge Emerson Buie, Jr. said it was investigating the case as a "potential assault on federal officers" and appealed to the public to call in with any tips.
Spokesman Douglas Mosier says Martinez was 36 years old and from El Paso. Martinez died from the injuries he suffered early Sunday morning. Martinez died and his unidentified partner is in serious condition.
Rush Carter, a supervisor for the U.S. Customs and Border Patrol region that includes the area where Martinez died, said all the agency can confirm is that the two "were injured while performing their regular duties".
Harper told the San Antonio Express-News on Sunday that Martinez and his partner were 'not fired upon, ' but she didn't elaborate.
Authorities did not provide any details Sunday on what caused the agent's injuries or what led to them. In any such investigation, the FBI would consider all possibilities-including that an accident was a fault or that an attack was to blame.
The official said it happened after dark in an area that's known for drug activity and where agents often look for drugs in culverts. His partner, who was injured, remains in the hospital in stable condition.
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.
A union spokesperson said the agents were attacked with rocks.
Few details have been released about the incident late on Saturday not far from the USA border with Mexico near Interstate 10, about 150 miles (240 km) southeast of El Paso. "As authorities continue their investigation, it is important that they receive any and all information to help apprehend and deliver swift justice to those responsible". "We will, and must, build the Wall!"
The FBI has taken over the investigation of the death of one U.S. Customs and Border Protection agent and the serious injury of another.
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