PHOENIX -- A prominent southeast Arizona rancher likely was killed by an illegal immigrant, but there's no evidence to suggest there was any confrontation that led to the shooting, authorities said Monday.
The body of Robert Krentz, 58, was located before midnight Saturday on his 35,000-acre ranch about 35 miles northeast of Douglas after his brother reported that he had lost radio contact with Krentz earlier in the day.
At a news conference Monday, Cochise County Sheriff Larry Dever said Krentz was out checking water line and fencing on the land Krentz's family has ranched since 1907. Krentz had weapons with him in his all-terrain vehicle but didn't use them, according to Dever.
Investigators said Krentz apparently came upon one person when he was shot. Krentz was heard telling his brother "illegal alien" on the radio earlier Saturday, and the area of the killing is a known smuggling corridor, according to authorities.
While Krentz was still in his vehicle, mortally wounded, he managed to drive the ATV away from the scene at a high rate of speed before becoming unconscious. The ATV still had its lights on and the engine running when authorities found it.
Foot tracks were identified and followed approximately 20 miles south to the Mexico border by sheriff's deputies, U.S. Border Patrol trackers and Department of Corrections dog chase teams, authorities said.
The sheriff's office said Krentz's body was transported to the Cochise County Medical Examiner's Office for an autopsy to determine approximate time of death.
So far, there have been no suspects identified and no arrests.
"We are assuming he escaped south into Mexico," Dever said of the shooter.
Dever told a Tucson newspaper that while investigators don't have a motive yet, retaliation has been raised as a possibility. The day before the shooting, the victim's brother, Phil Krentz, reported drug smuggling activity on the ranch to the Border Patrol.
Agents found 290 pounds of marijuana on the ranch and followed tracks to where they found and arrested eight illegal immigrants. All were still in custody when the shooting occurred, the Arizona Daily Star reported.
U.S. Rep. Gabrielle Giffords, D-Ariz., whose Congressional district covers the area, issued a statement saying Krentz's killing is a horrible tragedy that deserves a swift and strong response.
"The cold-blooded killing of an Arizona rancher is a sad and sobering reminder of the threats to public safety that exist in our border communities," Giffords said. "It has not yet been determined who committed this atrocity or why, but I know that federal and local authorities are mobilizing every possible resource to locate and apprehend the assailant."
Giffords said if Krentz's killing is connected to drug cartels or smugglers, the federal government must respond appropriately.
"All options should be on the table, including sending more Border Patrol agents to the area and deploying the National Guard," Giffords said.
Arizona Attorney General Terry Goddard said government has a clear responsibility to aid law enforcement resources at all levels along the border.
"I call on our federal and state governments to work together to bolster the law enforcement resources needed to better protect Arizonans living on the border," Goddard said.
"The federal government must do all it can within its power to curb this violence and protect its citizens from criminals coming across the border from Mexico," McCain wrote in a letter to Homeland Security Secretary Janet Napolitano, a former Arizona governor.
U.S. Sens. Jeff Bingaman and Tom Udall of New Mexico, along with Rep. Harry Teague, said Napolitano's agency needs to take more security steps and increase the Border Patrol's presence in the Boot Heel of New Mexico.