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Demonstrations and clashes with police continued for a third day in California after an 18-year-old man was gunned down by LA County sheriff's deputies while working as a security guard at an auto body shop.

"He ran because he was scared," one of the protesters' signs read as the crowd chanted, "Why'd you kill that kid?" during a protest on Sunday.

As protesters blocked traffic, a sheriff's helicopter circled overhead. "We don't want to see your children hurt," a voice announced from the helicopter.

He urged the protesters to leave the area so the women and children weren't exposed to pepper spray or tear gas.

The Los Angeles County Sheriff's Department confirmed a sheriff's deputy fired six shots at Andres Guardado during a foot pursuit at the rear of a car business at 420 West Redondo Beach Blvd on Thursday, June 18.

The incident happened shortly before 6 p.m., when two Compton Station deputies who were on patrol spotted Guardado talking to someone in a car that was blocking the driveway to the body shop.

Guardado reportedly looked at them, produced a handgun and fled southbound between two businesses.

The police stopped him at the rear of the car business and one of them fired six rounds at him, killing him.

A .40 caliber semiautomatic pistol with no markings or serial number was recovered near his body. The gun had been altered with an illegal, extended 15-round magazine with 13 live rounds in it, police say.

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Guardado's sister, Jennifer Guardado, 22, (pictured above), said her brother ran when he saw armed police because he was scared.

"He was going to have a great career and a family," she said Friday, according to The LA Times. "He'll never get to experience that. They took that away from him. I never got to say goodbye."

She said her brother was a hard-working teenager who held down two jobs and loved going to the gym. He was working at the auto body shop to get back into school.

But police say Guardado was not wearing a security uniform, nor was he wearing a gun belt or holster. He did not have handcuffs or a security badge.

The age requirement to work as a security guard in California is 21.

Guardado's family want an independent investigation into Guardado's murder.