A Border Patrol agent has been shot to death in Arizona near the US-Mexico line.
The killing, on Tuesday (local time), is the first fatal shooting of an agent since a deadly 2010 firefight with Mexican bandits that spawned congressional probes of a botched government gun-smuggling investigation.
The agent, 30-year-old Nicholas Ivie, and a colleague were on patrol in the desert near Naco, about 100 miles (160km) from Tucson, when gunfire broke out shortly before 2am, the Border Patrol said. The second agent was shot in the ankle and buttocks, but was reportedly in stable condition.
Authorities have not identified the agent who was wounded, nor did they say whether any weapons were seized at the site of the shooting.
At a news conference in Naco, an FBI official said the agency still was processing the crime scene and that it might take several days to complete. The FBI and the Cochise County Sheriff's Office, which is also investigating, declined to say whether investigators have recovered guns or bullet casings.
No arrests have been made, but authorities suspect that more than one person fired at the agents.
"It's been a long day for us but it's been longer for no one more than a wife whose husband is not coming home. It's been longer for two children whose father is not coming home, and that is what is going to strengthen our resolve" to find those responsible and enforce the law, said Jeffrey Self, commander of Customs and Border Protection's Arizona joint field command.
Ivie, who is married, lived in Sierra Vista with his wife and their two young daughters.
The last Border Patrol agent fatally shot on duty was Brian Terry, who died in a shootout with bandits near the border in December 2010. The Border Patrol station in Naco, where the two agents shot Tuesday were stationed, was recently named after Terry.
Terry's shooting was later linked 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 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 spectre those illegal weapons are still being used in border violence.