Just what happened in a remote area of West Texas Saturday night?

The search for answers continues after a U.S. Border Patrol agent was killed and his partner was injured.

Agent Rogelio Martinez died Sunday from injuries to his head, chest and collarbone. He and the second agent, who has not been identified, were found late Saturday in a culvert near Van Horn, Texas, not far from the Mexico border.

The surviving agent is in stable condition, but he apparently does not remember anything that happened. An internal Border Patrol email does not specify if they were attacked or if they fell into the culvert.

The National Border Patrol Council Union spokesperson called the situation an ambush.

"If you think about it there are at least one, maybe more murderers on the loose right now in our country that just murdered a Border Patrol agent and tried to murder another one -- so we need to find out who these people are and we need to bring them to justice," said Chris Cabrera of the National Border Patrol Council.