A 36-year-old Border Patrol agent died Sunday morning from injuries he sustained in an "attack" while on patrol along the southern border in Texas.

Update: A National Border Patrol Council (NBPC) official tells Fox News that Martinez and a second agent were "ambushed" by attackers. Brandon Judd, the president of the NBPC union, told Fox News on Monday it appeared Martinez and the second agent were “ambushed” by a group of illegal immigrants.

“We don’t know exactly what happened because we weren’t there. However, just from agents that were working in the area, reports are saying it was an attack and it would appear to be an ambush,” Judd said.

“There’s a high likelihood this was an assault on the agents," Judd added.

The U.S. Customs and Border Protection said in a statement the incident occurred when Rogelio Martinez and his partner, who was not identified and was also injured in the incident, were responding to "activity" while on patrol in the Big Bend Sector which runs along the southern border with Mexico.

The area falls in Culberson County in West Texas.

Martinez, who hailed from El Paso, had been a border agent since August 2013.  Martinez and his partner were assigned to the Big Bend sector, which covers 135,000 square miles in Texas and Oklahoma.

Both Martinez and his partner were rushed to the local hospital, where Martinez succumbed to his injuries while his partner is in serious condition.

According to an email from acting Border Patrol Commissioner Kevin McAleenan, posted by the Border Patrol Foundation, Martinez was found “unconscious, with multiple injuries to his head and body,” reported Heavy, a New York-based digital media company.

Border Patrol spokesman Carlos Diaz told the Washington Times that they were unable to provide details on what caused the agent’s injuries.

According to the Times, the authorities are searching the Big Bend area for potential suspects and witnesses after the incident was reported.

Diaz also said the FBI has taken over the investigation process

FBI spokeswoman Jeanette Harper said to CNN, “The FBI is still actively investigating the incident and gathering the facts.”

Sen. Ted Cruz (R-Texas), however, said in a statement that the agents were attacked.

The USA Today reported Cruz saying in the statement, “This is a stark reminder of the ongoing threat that an unsecure border poses to the safety of our communities and those charged with defending them. We are grateful for the courage and sacrifice of our border agents who have dedicated their lives to keeping us safe. I remain fully committed to working with the Border Patrol to provide them with all the resources they need to safeguard our nation.”

According to the Border Patrol records, between October 2016 and May 2017, the Big Bend accounted for about 1 percent of the more than 61,000 apprehensions that its agents made along the southwest border. The mountains in the region and the Rio Grande make it difficult for people to cross illegally into the U.S. from Mexico.

According to the CNN, the acting Secretary of Homeland Security Elaine Duke said in a statement, "On behalf of the quarter of a million front line officers and agents of DHS, my thoughts and prayers go out to the family and friends of Agent Martinez and to the agent who is in serious condition."

In response to the incident, President Donald Trump iterated his call to build a wall along the country's southern border and tweeted, “We will seek out and bring to justice those responsible. We will, and must, build the Wall!”