One of five people charged in the murder of a U.S. Border Patrol agent admitted Tuesday that the motivation behind the ambush killing was to rob the agent's night vision equipment.

Emilio Gonzales pleaded guilty to murder of a federal officer in court and faces life in prison when he is sentenced Oct. 17.

The San Diego Union-Tribune reported that Gonzales admitted in his plea agreement that he and two others crossed from Mexico to a remote mountainous area in Campo, east of San Diego, in July 2009 and left footprints in the dirt to lure an agent into a trap.

When Border Patrol Agent Robert Rosas followed the trio — Gonzales, Marcos Rodriguez and Christian Daniel Castro Alvarez — into the brush, they held him at gunpoint. Rosas resisted and was shot during a struggle.

The plea agreement said that the group stole Rosas' night vision device, bag, firearm, handcuffs and other items. The same month of the killing, Rodriguez lost a night vision device that he and others used to smuggle illegal immigrants and drugs into the United States.

Two others charged in the case — Jose Juan Chacon and Jose Luis Ramirez — are accused of staying in Mexico as armed lookouts.

Alvarez, who was 16 at the time of the killing, pleaded guilty to murder in San Diego for his role in the killing and was sentenced last year to 40 years in prison.

Ramirez has pleaded not guilty.

Rodriguez was arrested in Mexico in April and is expected to be extradited.

The fifth man, Chacon, remains at large although suspects have told Mexican authorities that he is dead.


Information from: The San Diego Union-Tribune, http://www.signonsandiego.com