Alberto Alvarez moved aggressively forward while East Palo Alto Police Officer Richard May retreated in the seconds before Alvarez fatally shot May, a witness said Tuesday morning.

Virginia Rodriguez, a petite, Spanish-speaking woman, provided compelling testimony and the most complete picture yet of May's shooting death on Jan. 7, 2006, in East Palo Alto.

Through an interpreter, Rodriguez told a San Mateo County Superior Court jury that she saw two men struggling in a driveway on Weeks Street as she looked out her apartment living room window.

Alvarez is on trial to determine whether he "executed" May as alleged or was responding defensively to an aggressive police pursuit. His attorneys have stipulated that he killed May, but the outcome could determine whether he might receive the death penalty or up to life in prison.

Rodriguez said at first she thought the men were playing or fighting.

She said the man she later identified as Alvarez moved between two cars -- a white truck and an older Oldsmobile parked in the driveway at 579 Weeks, three doors up and across the street from her apartment.

He went toward the house and moved into the corner between the front bumper of the Oldsmoblie and the garage door, she said.

May also moved between the cars but went only a short distance toward Alvarez, she said.

Alvarez then moved toward May, who backed up behind the cars, closer to the street, she said.

Alvarez advanced toward the officer, to the middle of the driveway between the cars, near the truck's back bumper.

"They were within arm's reach of each other. They tried to grab each other again. I saw the second person (May) take some steps back. He went backwards and fell backwards. ... He fell on his back," she said.

Rodriguez said she then noticed May was wearing a badge and realized he was a police officer.

Her children entered the apartment and said they heard gunshots, she said.

Rodriguez said she saw Alvarez start to leave and go toward the street.

"Then he came back and shot (May) again," she said.

Alvarez stood at May's feet as the officer lay on the pavement and pointed his arm at a 45-degree angle toward May's upper body and fired more than one shot, she said.

"You could see a pool of blood after, ... a whole lot of blood," she said.

On cross examination, Rodriguez gave confusing testimony about whether she heard the first barrage of shots or was told by her children.

Defense Attorney Charles Robinson tried to challenge her testimony and called into question conflicting statements she made to a grand jury and to inspectors.

"What you told the officers that night was the truth?" he asked.

"Yes. But on that piece of paper there were a lot of things I didn't say," she said, referring to her police statement.

"Did it look to you like the man was trapped?," he asked. Rodriguez said it did.