More questions than answers remain as investigators search for clues in how a Border Patrol agent was killed and his partner suffered severe head trauma.
The FBI believes the two agents were probably attacked and not involved in an accident. Rogelio Martinez, 36, died Sunday after sustaining severe head and bodily injuries.
But other possibilities remain on the table. One theory is that illegal immigrants armed with rocks attacked the agents outside of the town of Van Horn in South Texas.
Another theory suggests the agents fell into a ditch, the New York Daily News reported.
Martinez and his partner were found around 11 p.m. Saturday in the Big Bend area outside of Van Horn, according to a statement from the FBI. The second agent's identity has not been released. The injured agent managed to radio for help but has been unable to remember any details, according to reports Tuesday. He is still listed in critical condition.
The FBI is unlikely to release any details until its investigation is concluded, reports stated.
"If the FBI started jumping into that speculation right now, it would really ruin the integrity of the investigation," said Gregory Vecchi, a federal agent in four agencies over 29 years.
FBI agents are continuing to interview everyone involved in working with the Border Patrol. The are also examining rocks for blood and hair to determine if rocks were used to commit the crime.
Officials are offering a $25,000 for anyone with information leading to a criminal arrest.