A U.S. Border Patrol agent and his brother are standing trial in Texas in the killing of a man who prosecutors say threatened to uncover their trafficking of weapons and drugs.
The agent, 31-year-old Joel Luna, and his brother, 26-year-old Eduardo Luna, have pleaded not guilty to murder and other charges.
A third brother testified Wednesday that he saw Eduardo Luna fatally shoot an associate in early 2015. The man's headless body was found floating off the Texas coast in March that year.
Prosecutors contend Joel Luna used his position to help a Mexican cartel move illegal weapons and ammunition south of the border and drugs to the north. The agent's lawyer has denied he had any involvement in the illicit activity.