ANAHEIM (CBSLA) — A replica handgun designed to resemble a Berretta pistol was recovered from the scene of a shooting involving a Fullerton police officer that left a 17-year-old girl dead, prosecutors said Tuesday.

Hannah Linn Williams, 17, of Anaheim, was fatally shot Friday night during a traffic stop Friday night on the eastbound 91 Freeway, just west of Tustin Avenue in Anaheim.

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The gun was found in the vehicle next to Williams, according to the Orange County District Attorney Todd Spitzer.

Prosecutors say the on-duty Fullerton police officer was in full uniform while driving in his marked police SUV on the eastbound 91 freeway while taking his police K-9 to the veterinarian for a medical procedure. He then saw Williams, who was also headed eastbound on the 91 freeway at a high rate of speed, near Glassell Avenue, according to Spitzer.

At some point and for reasons that were not disclosed, the two vehicles came into contact, at which point the officer-involved shooting occurred. Investigators found a replica Beretta 92 FS handgun at the scene next to the female.

At a news conference Tuesday, Williams’ family and community activists called for a full investigation into the shooting, including an independent autopsy.

“It was a rental car, this is a young lady who had several siblings, and we don’t know who that gun belonged to,” said community activist Rev. Jerret Maupin.

Family members say they weren’t sure where Williams was headed Friday night before the encounter with police, but they maintain it’s out of her character to carry a replica gun.

“We maintain she was unarmed,” said Maupin. “A fake gun is a fake gun.”

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Prosecutors say this replica handgun was designed to look like a real Beretta. (Photo via OCDA)

It is illegal to possess a replica handgun in the state of California.

The Fullerton police officer reported the shooting just after 7 p.m. Friday, according to Anaheim Police Sgt. Daron Wyatt. Williams was rushed to a hospital, where she was pronounced dead.

The circumstances of the traffic stop have not been released. But video from the scene immediately after the officer-involved shooting show detectives examining a U-Haul truck on the side of a road. The eastbound lanes of the freeway were shut down for several hours for the investigation.

Hannah Linn Williams was fatally shot Friday night. (credit: CBS)

Coverage of the officer-involved shooting was overshadowed by the magnitude-7.1 earthquake that hit Ridgecrest about an hour later. Williams’ family, along with leaders from the National Action Network and NAACP, will hold a news conference Tuesday to demand Gov. Newsom order a civil rights investigation into the shooting.

“The Williams Family wants to set the standards for transparency in this case,” Rev. Jarrett Maupin of the National Action Network said in a statement. “The public wants to know what happened and whether or not the officers involved followed all policies and procedures. We have doubts.”

The Orange County District Attorney’s office and Anaheim police are leading the investigation into the shooting. Fullerton police will conduct a separate administrative investigation.

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The officer is on paid administrative leave.