By Tim Gaynor
PHOENIX (Reuters) - A U.S. Border Patrol agent was shot dead by suspected smugglers close to the Mexico border in southern Arizona and four suspects have been arrested, authorities said on Wednesday.
Agent Brian A. Terry, 40, was shot dead after he confronted several suspects while on duty in a mountainous area a few miles northwest of the border city of Nogales late on Tuesday night, local and federal police said.
Police arrested at least four suspects, and are searching for another who remains at large, the Santa Cruz County Sheriff's Office and U.S. Customs and Border Protection agency said.
"Our thoughts and prayers are with the Terry family for their tragic loss," CBP Commissioner Alan Bersin said in a statement.
"Our commitment to Agent Terry and his family is that we will do everything possible to bring to justice those responsible for this despicable act," he added.
Arizona Governor Jan Brewer ordered state flags flown at half staff in tribute to Terry, a Marine Corps veteran from Detroit, Michigan, who served in the Border Patrol's Tucson sector.
Agents patrolling the sector's 262-mile stretch of the Mexico border make around half of the illegal immigrant arrests and marijuana seizures recorded along the southwest border.
Santa Cruz County Sheriff Tony Estrada said the assailants were likely smugglers who use the rugged, mountainous area west of Nogales to haul both drugs and illegal immigrants into the United States.
"That area is known to be a smuggling area, both human and drug smuggling, so it was either one of the two more likely," Estrada told Reuters.
The FBI is leading the investigation into the agent's death, with the assistance of the Santa Cruz County Sheriff's Office.
The last Border Patrol agent to be killed on duty was Robert Rosas, 30, who was shot to death near Campo in southern California in July 2009. Police caught the killer, who was subsequently jailed for 40 years.
(Editing by Jerry Norton)