BISBEE - A surveillance video of a Jan. 12 deadly Border Patrol shooting in the desert near Naco shows Agent Nicholas Corbett circling his SUV around a small group of people before stopping, getting out and dashing around the back of the truck.

Without pausing, Corbett, easily identifiable in the otherwise grainy, long-distance video thanks to his dark green Border Patrol uniform, emerges from behind the truck and charges up to the group, who are now less than 10 feet from the vehicle's right rear bumper. When Corbett reaches the subjects, a body - presumably that of 22-year-old Francisco Javier Dominguez-Rivera - is thrust forward.

Dominguez-Rivera, a native of Puebla, Mexico, who had crossed illegally into the United States just minutes earlier, was shot and killed during the confrontation.

The entire sequence, from when Corbett exits his truck to when he reaches the group, lasts no more than four seconds.

What follows is slightly more than a minute of Corbett remaining near the group, sometimes standing, sometimes crouching, before a second green-uniformed agent, later identified as Stephen Berg, approaches.

Approximately 10 minutes after the initial confrontation, at 3:29 p.m., the camera, stationed on a Border Patrol video tower approximately two miles away, zooms in and the picture improves dramatically. One agent is crouching, another is standing, and both are looking at what appears to be a body lying in front of them.

Just a few feet away, three people - two of Dominguez-Rivera's brothers and his sister-in-law - are sitting motionless on the ground.

The video, released Tuesday by Cochise County Attorney Ed Rheinheimer in response to a public records request by the Herald/Review and the Arizona Daily Star, is the latest piece of evidence to cast doubt on the Border Patrol's initial account of the shooting.

On Monday, Rheinheimer turned over to reporters nearly 300 pages of documents from an investigation by the Cochise County Sheriff's Office. Among the evidence were memos from three field operations supervisors at the Border Patrol's Naco Station who said Corbett told them he shot Dominguez-Rivera after he threatened him with a rock.

In one memo, written by Agent Murray Adams, Corbett reportedly fired after facing off with Dominguez-Rivera from the opposite end of his truck. In an account from Agent Rick Carranza, Corbett chased Dominguez-Rivera around the truck before Dominguez-Rivera turned and faced him with a rock. And in a third memo, Corbett reportedly told Agent Diego Granillo that Dominguez-Rivera shadowed him from the opposite side of the truck before confronting him with the rock.

"An individual yielding a rock and making a threatening movement threatened him," Carranza wrote. "Fearing for his safety, Agent Corbett fired one round."

In all the memos, Corbett was facing Dominguez-Rivera when he shot him straight on in the chest. An autopsy report, however, showed the bullet followed a sharp downward trajectory after entering the victim's upper left chest, suggesting Corbett had been standing over Dominguez-Rivera when he fired.

A crime lab test on Dominguez-Rivera's shirt showed the shot was fired from a distance between 3 inches and 2 1/2 feet.

The three members of Dominguez-Rivera's group told investigators that Corbett, pistol in hand, ran from his truck directly at Dominguez-Rivera, who was the only member of the group who had not taken a kneeling position.

The witnesses said Corbett hit or punched Dominguez-Rivera in the back of the neck with his right hand, forcing him to his knees. Corbett then shot him at point-blank range with his left hand.

Details difficult to see

The relevant portion of the surveillance video begins just after a timestamp of 3:19 p.m., when a white Border Patrol SUV enters a previously still picture showing the city of Douglas in the distance and an empty desert in the foreground.

The SUV drives north from the clearly identifiable border access road for approximately 15 seconds before making a tight loop back toward the south, on the right side of the screen.

At the same time, a group of four people emerges from off camera on the left side of the picture. The group moves briefly in a southern direction, toward Mexico, before stopping next to the truck.

The vehicle remains motionless for a few seconds and its driver's side door appears to open slightly. It then moves forward approximately 10 feet before stopping again. The door opens wider and Corbett runs around the back.

In a report released Monday, Sheriff's Office detective Mark Genz, who viewed the recording two days after the shooting, said he saw Corbett exit his SUV and approach the group.

"It appears that one of the subjects he is near goes down partly, possibly to his knees, and then goes to the ground all the way and you lose sight of him," Genz wrote.

None of the Herald/Review staff members who viewed the recording Tuesday could see the same level of detail. While a body seemed to have been thrust forward once Corbett reached the group, it was impossible to determine if the person fell to his or her knees.

Carol Capas, spokeswoman at the Sheriff's Office, was unsure if Genz had seen a higher-resolution recording than the digital video files released Tuesday. Genz was not at work and could not be reached for comment, Capas said.

Rheinheimer said the FBI is currently working to enhance the original video. He won't decide whether to charge Corbett until the FBI returns the improved tape, he said.

Corbett, who was returned to full duty at the Naco Station following an internal review by the Border Patrol, declined to be interviewed by investigators. Telephone and e-mail messages left with his lawyer, Daniel Santander, were not returned Tuesday.

Mike Albon, spokesman for the Border Patrol agent's union in the Tucson Sector, declined comment, citing the ongoing investigation.