(KWES) - UPDATE: Chris Cabrera, a spokesman for the National Border Patrol Council Labor Union, told us that Martinez was hit several times in the head with a blunt object, possibly a large rock.
Cabrera stated that agents being injured with rocks is very common.
We confirmed with the Council added that illegal aliens were involved in the incident.
"We've had agents, a good friend of mine actually almost lost his eye. It happens quite a bit, unfortunately," Cabrera told NBC News, adding that patrol vehicles, including helicopters, have been damaged by the throwing of rocks.
Cabrera said the type of rocks that agents are struck with are large in size, approximately as big as a grapefruit or softball.
"It's nothing to laugh at," he told NBC News. "It's something that will physically and permanently disfigure you, if not kill you."
A U.S. Border Patrol agent is dead and another is recovering following an incident while on patrol.
We're told Agent Rogelio Martinez and his Big Bend Sector partner were responding to activity while on patrol near Interstate 10, in the Van Horn Station area.
Agent Martinez's partner reported that they were both injured and in need of assistance.
Responding agents provided immediate medical care, and transported both agents to a local hospital.
The Big Bend Sector later learned that Martinez died from his injuries.
His partner remains in the hospital in serious condition.
Border Patrol agents from Big Bend Sector and the Culberson County Sheriff's Department secured the scene. The Border Patrol's Special Operations Group and agents from CBP's Air and Marine Operations are searching the area for potential suspects or witnesses.
The Culberson County Sheriff's Department, Federal Bureau of Investigation, Office of Inspector General, and CBP's Office of Professional Responsibility are investigating.
Condolences have already been posted on social media following the incident. Those posting on social media include President Donald Trump.