Yannelli declined to say what the girl's relationship with Garcia-Juaregui was, but confirmed that the two are not family members.
Police believe that Garcia-Juaregui shot and killed Wride after the officer stopped his patrol car to check on a pickup with flashers blinking on State Road 73. The teen girl was in the truck with Garcia-Juaregui, who allegedly shot Wride while he was in his patrol car, before fleeing south to Santaquin, where he encountered Deputy Greg Sherwood, 38, who was shot and wounded in the head.
Later that day, Garcia-Juaregui was wounded during a gun fight with Juab County Sheriff's officers on Interstate 15 south of Nephi. He died the next day at a hospital.
Yannelli said officials don't believe at this time that the teen girl fired any shots at police officers.
"That's what we are waiting for the video enhancement to show, really," he said. "[But] it didn't appear that she was the active shooter, no."
Yannelli said the teen is currently being held in a juvenile detention facility in Provo. There is a time limit to how long authorities can hold a teen in custody without filing charges, Yannelli said, but that time can be extended if a judge authorizes it.
The teen is scheduled to make an appearance in juvenile court in Provo on Friday morning, where prosecutors will ask the judge for that extension in order to have time to sort through the evidence before possibly filing charges.
The girl's attorney, Neil Skousen, did not return phone calls seeking comment Thursday.
If charges are filed against the teen, it has not yet been decided whether they will be filed in Utah or Juab County. Juab County Attorney Jared Eldridge would not comment about the juvenile suspect on Thursday.
Yannelli would not disclose much additional information about the teenager, but said she was living in Utah at the time of the shooting.