A National Park Service ranger at Organ Pipe Cactus National Monument was killed in a shootout with suspected smugglers Friday afternoon, said deputy Nicole Feldt of the Pima County Sheriff's Department.
At least one other man, believed to be a Mexican citizen, was also shot and killed and another was in custody, said Edward "Bud" Tuffly, president of the union of Border Patrol agents in Southern Arizona.
The ranger's identity was being withheld Friday pending family notification.
Mexican officials said the shooting is linked to a quadruple murder that occurred in Mexico on Thursday.
Thursday night, federal police arrested a 19-year-old who said he had participated in the contract murder of four people, said Miguel Francisco Lopez Castro, regional head of the Sonoran Attorney General's Office.
The man, Jesus Martin Yescas Zazueta, said he had come from Tijuana to carry out those killings and others for someone nicknamed "El Zarco," Lopez Castro said.
About 9 a.m. Friday, police found the four bodies about 10 miles west of Sonoyta, Lopez Castro said. Three of the victims had their arms tied behind their backs and a gunshot to the head. The other victim was untied and shot multiple times.
After that discovery, 60 officers were called in from around Sonora to look for the suspected mastermind and avert further confrontations between the hit men and their remaining targets.
Officers found "El Zarco," whose real name is Panfilo Murillo Aguila, about 1 p.m. Friday just southeast of the Lukeville port of entry.
Shooting ensued, and Mexican officials called authorities to warn them Murillo Aguila and a companion were heading north.
The ranger who was killed and Border Patrol agents were in the area when Murillo Aguila and the companion reached the border. The ranger was responding with U.S. Border Patrol agents to a call for assistance from Mexican authorities about three miles east of Lukeville, according to Dale Thompson, chief park ranger at Organ Pipe National Monument.
It's unclear whether it was Murillo Aguila or his companion who was killed by the gunfire. The survivor was arrested by U.S. authorities.
The incident is under investigation by the Pima County Sheriff's Department and the FBI, which did not return phone calls to its Phoenix office Friday.
Reports of the shooting's exact location varied, but Feldt said it took place near Puerto Blanco Loop Drive, a dirt road that runs through the national monument west of Arizona 85.
U.S. Border Patrol spokesman Ryan Scudder in Tucson confirmed that U.S. Border Patrol agents were on the ground and in a helicopter overhead when the shooting occurred, but referred all other questions to the Sheriff's Department and FBI.
Tuffly said a Border Patrol agent and the ranger were together on foot, although not necessarily near one another, when the shooting occurred.
"He was helping the Border Patrol and got shot for it," Tuffly said. "They help us out a lot when they can, but that's not part of his job description, interdicting smugglers down by the port of entry. But if we need backup, they'll help us out. It's real unfortunate."
The park ranger, a commissioned law enforcement officer, was armed and wearing body armor at the time, Thompson said.
He said the weapon that killed the ranger was a rifle. The ranger was one of four Park Service rangers assigned to the Organ Pipe Cactus National Monument.
In Washington, the National Park Service released a statement: "We regret to inform that an NPS law enforcement ranger was shot and killed in the line of duty this afternoon while pursuing two armed suspects along the U.S.-Mexican border. We will provide further details when they become available."
* The Associated Press contributed to this report.
* Contact reporters Ignacio Ibarra at (520) 432-2766 or nacho1@mindspring.com and Tim Steller at 434-4086 or steller@azstarnet.com.