NORWALK (CBS) — A 21-year-old man was convicted today of murder for shooting a Pico Rivera woman to death after she interrupted a gang member spraying graffiti near her home, but the jury acquitted his two co-defendants.

Angel Chris Rojas was found guilty of first-degree murder in the death of Maria Hicks, 58, shooting at an occupied vehicle, street terrorism and unlawful firearm activity, along with an allegation that he committed the crimes to benefit a Pico Rivera gang called the Brown Authority. He faces at least 50 years to life in prison at his sentencing March 16.

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However, the co-defendants — Jennifer Ann Tafolla, 24, and Richard Daniel Rolon, 25 — were convicted only of street terrorism. They will be sentenced Feb. 24.

The prosecution alleged that on Aug. 10, 2007, Rojas — who was 16 at the time — shot three to five rounds at the Honda Element being driven by Hicks after she flashed her headlights and honked her horn at Cesar Lopez, another Brown Authority member who was spray-painting graffiti on a wall at San Gabriel River Parkway and Woodford Street.

Rojas, who was riding in a Lincoln Continental being driven by Tafolla, was accused of getting out of the car to shoot at Hicks. Rolon was another passenger in the vehicle.

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Hicks was hit once in the head and died three days later.

During the trial, a detective who works in the sheriff’s department’s gang unit, said he would expect a confrontation to result if a civilian tried to stop a gang member from spraying on graffiti.

Rojas’ lawyer argued that he thought he was protecting Lopez from rival gang members when he shot at Hicks’ vehicle.

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Lopez, who accepted a plea agreement, is awaiting sentencing.