By Ronnie Cohen

SAN FRANCISCO (Reuters) - The FBI has launched an independent investigation into a deputy sheriff's killing of a 13-year-old boy while he was walking to a friend's house this week to return a replica of an assault rifle, a spokesman said on Saturday.

Sonoma County Sheriff Steve Freitas announced on Friday night that the FBI will conduct an inquiry into the shooting death of Andy Lopez Cruz in Santa Rosa, a community in northern California's wine country.

Hundreds of protesters, many of them Latino teenagers, have demonstrated daily, calling for an investigation into the Tuesday afternoon incident in a blue-collar neighborhood of Santa Rosa.

While the Santa Rosa Police Department and other local agencies continue to investigate the shooting, civil rights advocates have sought an independent federal investigation.

The FBI's San Francisco office will "review all the facts and see if there was any federal crime committed, whether the individual's civil rights were violated," said spokesman Peter Lee.

Freitas said he welcomed the FBI probe into the death of the popular eighth-grader who played the trumpet and basketball and enjoyed teasing friends.

The deputy, a 24-year veteran of the force, saw Andy carrying what he believed was a real rifle, feared for his life and fired eight shots at the hoodie-clad boy as he walked along a vacant lot about a block from his family's mobile home, authorities said.

The tragedy is the latest in a number of police shootings involving people with toy weapons and has reignited calls in Sonoma County to create a civilian review board to examine such incidents.

Police said the boy had his back to the deputy and a deputy trainee, both of whom commanded him to drop the gun as they crouched behind the door of their patrol car.

When Andy turned toward them with the gun still in his hand, the veteran deputy began firing from a distance of 20 to 30 feet, officials said.

Seven bullets struck Andy; two of the rounds were fatal.

Story continues

Andy's father, Rodrigo Lopez, said he believes his son may not have heard the deputies' orders.

"I think he would have done what they told him," he said. "I know him, and he has respect for the law, for police."

A police spokesman told the Santa Rosa Press Democrat newspaper that it remained unclear whether Andy, who enjoyed listening to music, was wearing ear buds at the time.

No more than 10 seconds elapsed from the time the deputies spotted the boy carrying what they believed to be an assault rifle and the moment they shot him dead, police said.

Because of social media threats leveled against the two officers, the sheriff said he would not release their names at this time. Both have been placed on administrative leave.

Andy's parents said a friend left the plastic assault rifle at their home last weekend, and he was on his way to the friend's house to return it after school when he was shot.

An orange tip that is required to be placed on imitation air guns apparently had been removed from the one Andy carried.

"They didn't have the right to kill him," Andy's distraught friend, Magaly Bejaran, 13, told Reuters.

(Reporting By Ronnie Cohen; editing by Gunna Dickson)