Border Patrol agent killed on duty in Ariz.

NACO, Ariz. -- A Border Patrol agent was shot to death yesterday and his partner wounded near the U.S.-Mexico line, the first fatal shooting of an agent since a 2010 firefight with Mexican bandits that spawned congressional probes of a botched gun-smuggling investigation.

The agent, Nicholas Ivie, 30, and an unidentified colleague were on patrol in the desert near Naco, about 100 miles from Tucson, when the shooting broke out shortly before 2 a.m., the Border Patrol said. The second agent was shot in the ankle and buttocks, and was in stable condition.

At a news conference in Naco, an FBI official said the agency was processing the scene. The FBI and the Cochise County Sheriff's Office declined to say whether guns or bullet casings were recovered.

Authorities suspect that more than one person fired at the agents.

The last Border Patrol agent fatally shot on duty was Brian Terry. He died in a shootout with bandits near the border in December 2010. The Border Patrol post in Naco, where the two agents shot yesterday were stationed, was recently named after Terry.

Terry's shooting was linked later to the government's "Fast and Furious" gun-smuggling operation, which allowed people suspected of illegally buying guns for others to walk away from gun shops with weapons, rather than be arrested. Authorities had intended to track the guns into Mexico.

Two rifles found at the scene of Terry's shooting were bought by a member of the gun-smuggling ring being investigated.

Critics of the operation say any shooting along the border now will raise the specter those illegal weapons are still being used in border violence.

"There's no way to know at this point how the agent was killed, but because of Operation Fast and Furious, we'll wonder for years," Republican Sen. Chuck Grassley said.

Thousands of sensors along the border, when tripped, alert dispatchers to send agents to that location. The agents were fired upon as they responded to an alarm triggered on one of the sensors, said sheriff's spokeswoman Carol Capas.