NORWALK — A judge sentenced a 24-year-old man to 21 years in prison Thursday for his role in the slaying of a Pico Rivera grandmother who tried to stop him and three accomplices from tagging on a wall near her home.

Cesar Lopez received his sentence from Norwalk Superior Court Judge Dewey Falcone. He had pleaded no contest to a voluntary manslaughter charge with gang enhancements in exchange for his testimony against the other three defendants in the Aug. 10, 2007 shooting death of 57-year-old Maria Hicks.

Co-defendants Angel Rojas, 21, Jennifer Tafolla, 24, and Richard Rolon, 25, have also been convicted for their roles in the incident on San Gabriel River Parkway and Woodford Street in Pico Rivera.

Rojas was convicted of first-degree murder, shooting at an occupied vehicle, street terrorism and unlawful firearm activity. The jury also found true special allegations that the crime was done for the benefit of a street gang, Brown Authority, and that he personally fired the bullet that killed Hicks.

Rojas could face life in prison when he returns to court for sentencing April 25, official said.

Tafolla and Rolon were convicted of street terrorism, which carries a maximum sentence of three years, and released on time served.

Lopez had crossed out another gang’s graffiti on a wall when Hick’s spotted the vandalism and flashed headlights at the four suspect, according to investigators. Rojas then opened fire on Hick’s car, striking her in the head.