President Donald Trump is renewing his demand that Congress fund a wall on the southern border after a U.S. Border Patrol agent was killed from injuries inccurred while working over the weekend in southwest Texas, while his partner was injured.

“Border Patrol officer killed at southern border, another badly hurt,” the president said in a tweet. “We will seek out and bring to justice those responsible. We will, and must, build the wall!”

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! — Donald J. Trump (@realDonaldTrump) November 20, 2017

Border Patrol Agent Rogelio Martinez, 36, and his partner were responding to “activity” in Van Horn, Texas. Martinez died and his partner, not named by officials or in news accounts, is reportedly hospitalized. News reports Monday morning said the government hasn’t confirmed what the agents were responding to.

The cause of death is not known. Jeanette Harper, with the FBI’s El Paso, Texas, office told the San Antonio Express-News: “They were not fired upon. There are so many different agencies working together that we need to come together and develop a timeline.”

CBP tells us Agent Martinez’ hometown was El Paso. He was 36 and entered on duty with the Border Patrol on 8/12/2013. pic.twitter.com/f9p1jzO7wW — Ashley Claster (@ClasterKFOX_CBS) November 19, 2017

“Earlier this morning, I was notified that Border Patrol Agent Rogelio Martinez died as a result of serious injuries suffered while on patrol in the Big Bend Sector of our southern border in Texas,” acting Secretary of Homeland Security Elaine Duke said in a public statement. The Border Patrol is a division of the Department of Homeland Security.

Duke continued:

Agent Martinez was responding to activity while on patrol with another agent, who was also seriously injured. We are fully supporting the ongoing investigation to determine the cause of this tragic event. On behalf of the quarter of a million frontline 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.

Texas Gov. Greg Abbott also weighed in.