A young volunteer firefighter wept on the stand Wednesday as he described coming to the aid of a Yolo County sheriff's deputy who lay mortally wounded on a dirt road near the rural community of Dunnigan.

Deputy Jose Antonio Diaz had been shot in the chest by a high-powered assault rifle on the night of June 15, 2008.

The deputy struggled to speak and breathe, and his condition quickly deteriorated as paramedics worked on him, said Brian Hunt, a volunteer with the Dunnigan Fire Protection District who testified in Yolo Superior Court in Woodland.

"He was talking to his partner and asking him to call his wife for him," Hunt said. Diaz repeated the plea 20 to 30 times, he said. Hunt, who was 19 at the time, broke down in tears as he recalled the chaotic minutes after the shooting.

Jurors heard his testimony - and watched a dashboard camera video of paramedics' rescue efforts – during the opening day of the penalty phase in the capital murder trial of Marco Antonio Topete.

Last week, jurors took less than a day to find Topete guilty of all the charges against him, including first-degree murder with the special circumstances of lying in wait and murder to avoid arrest.

The same jurors must also decide if Topete, 39, should be executed or spend the rest of his life in prison without the possibility of parole for the murder of Diaz, who was 37 when he died.

The penalty phase is expected to last two weeks.

Topete, a parolee with a history of violence, led Diaz on a high-speed chase, then ambushed him with an AR-15 assault rifle on an isolated county road, prosecutors told jurors in the trial's guilt phase.

On Wednesday, they opened their penalty-phase case with two witnesses who were among the first responders to the shooting.

Hunt said he was at home with his family in Dunnigan when a police car raced by. Minutes later, his pager went off. It was a medical call, "officer down," he said.

With other firefighters, he went to the scene and saw a patrol car quickly backing up. The deputy at the wheel stopped, and firefighters found Diaz wounded in the back seat.

They unloaded him and laid him on the edge of the county road, beside a dusty field. Stripping off his shirt and protective vest, they found a single bullet hole in his upper chest, Hunt said.

An ambulance soon arrived and Diaz was loaded on board. Meanwhile, firefighters set up a landing zone for a medical helicopter that was on its way.

The helicopter was about to land, Hunt said, but the ambulance raced past it and continued to Woodland Memorial Hospital, where Diaz died, he said.

Jurors saw photographs Wednesday of Diaz's body at the hospital. Bruce Naliboff, the district attorney's chief investigator, testified he arrived at the emergency room as doctors were performing open chest compressions on Diaz, to no avail.

Earlier in the day, sheriff's Deputy John Campos, Diaz's shift partner, took the stand and also broke down in tears. He said he had suffered from depression and struggled to do his job in the wake of Diaz's death.

During slow times, Campos said he and Diaz would park their cars side by side and talk. Diaz liked to talk about his children, he said.

"I don't think I ever saw him in a bad mood," Campos testified. "He was just always happy. Just a mellow guy."

On June 15, dispatchers issued a be-on-the-lookout bulletin for Topete, whom a 911 caller had seen drinking in Davis and getting behind the wheel with his infant daughter in the car. Topete might be heading toward his parents' home in Arbuckle, the dispatcher said.

Diaz decided to go to Dunnigan to look for Topete's blue Ford Taurus, Campos said. Campos said he would meet him there later.

At about 9:30 p.m., Diaz radioed he had spotted Topete at a truck stop in Dunnigan and was in pursuit. Campos, who was 17 miles away in Knights Landing, raced along rural roads to help.

He heard Diaz say Topete had abandoned his vehicle and fled on foot. Diaz was planning to check on the baby, who was still in Topete's car, Campos said.

For a time, there was radio silence. Then Diaz came back on and said he'd been shot, Campos said.

"It wasn't yelling," he said. "It was just a whisper."

What did you hear? District Attorney Jeff Reisig asked.

"Officer down," Campos said, weeping, "in such a low tone it wasn't normal."

© Copyright The Sacramento Bee. All rights reserved.

• Read more articles by Hudson Sangree

Order Reprint