SANTA ANA -- Surveillance video that shows Fullerton police officers kicking, punching and repeatedly using a stun gun on a homeless man provides clear-cut evidence that two of the officers are responsible for his death, a prosecutor told jurors Tuesday in closing arguments.

Orange County District Attorney Tony Rackauckas repeatedly replayed clips from the 33-minute, black-and-white video at the center of the murder and manslaughter trial. In it, 37-year-old Kelly Thomas cries out repeatedly for his father, apologizes and says he can't breathe as six officers pile on him.

Friends and family members of Thomas sobbed as the video played on a large screen. One woman dashed out of the courtroom, her hand over her mouth.

"As you watch, you realize that what you're watching and hearing is a person dying at the hands of the police," Rackauckas said. "You're watching a homicide."

Former Fullerton Officer Manuel Ramos, 39, has pleaded not guilty to one count of second-degree murder and one count of involuntary manslaughter. Former Cpl. Jay Cicinelli has pleaded not guilty to one count of involuntary manslaughter and one count of excessive use of force.

A third officer will be tried separately. Three others were not charged.

It's rare for a police officer to be charged with murder for actions taken in the line of duty -- and unheard of before now in conservative Orange County. Rackauckas, a four-term district attorney, has handled much of the trial himself -- an indication of its importance.

The July 2011 death of Thomas galvanized activists, who dubbed themselves "Kelly's Army," and led to the recall of three Fullerton City Council members and the departure of the police chief. Dozens of people have attended the trial each day wearing yellow ribbons and buttons bearing Thomas' image.

The confrontation began with a routine call about a disheveled man jiggling the door handles of cars in a transit center parking lot.

The video begins shortly after Ramos pulls up, and he can be heard trying to get Thomas to give his name and sit on the curb with his hands on his knees while another officer searches his backpack. Thomas was shirtless and had a huge, bushy beard and baggy pants.

When Thomas didn't comply, Ramos put on a pair of Latex gloves, made two fists and told Thomas, "Now you see my fists? They're getting ready to (expletive) you up."

Thomas stood up and started to run but was overtaken by the officers, who called for backup as the struggle with Thomas grew.

Cicinelli, who arrived shortly after the incident began, struck Thomas eight times in the face and head with a stun gun and stunned him repeatedly, according to prosecutors.

Defense attorneys will deliver their closing arguments in the monthlong trial when the prosecution is done.

Ramos had seven previous encounters with Thomas, who had also been written up for trespassing, urinating in a fountain, punching someone in the face, throwing large rocks and threatening the owner of a fruit stand with a metal pipe.

Thomas' father has said his son suffered from schizophrenia.

On Tuesday, Rackauckas told jurors that Ramos was fed up with dealing with Thomas and lost his temper. He signaled his intent to harm Thomas when he put on the gloves and made fists without saying he was going to arrest Thomas.

"Can you imagine that? Can you imagine having a police officer saying something like that when you're sitting there?" he asked the jury, adding that Thomas reacted in self-defense. "What does that mean? That means, 'I'm going to beat you up severely. There's going to be injuries here.'"

The coroner listed the cause of death as asphyxiation from the officers piling on his chest during the struggle.

Defense attorneys countered during trial that Thomas suffered from a weakened heart from years of methamphetamine abuse and was a mentally unstable and violent man who had abused drugs since 10th grade.

A forensic pathologist testified that the individual cells in Thomas' heart had changed size and shape because of the drug abuse and had microscopic scarring. Thomas' heart weighed 20 to 25 percent more than it should have for a man his age and size, the witness said.

Prosecutors countered with experts who found that Thomas' heart was healthy and the normal size for a man his size and age, and blood tests at the hospital showed he suffered from severe lack of oxygen.

Blood tests showed no alcohol or drugs in Thomas' system on the day of the struggle.