Also undetermined was the exact nature of the girl's relationship to Garcia-Jauregui, though police have confirmed they were not related.
"We're still trying to chase down the nature of their relationship. Detectives are interviewing her family and friends about that," Taylor said.
The girl was taken into custody on Jan. 30 unharmed, after the stolen pickup truck she was in with Garcia-Jauregui crashed on Interstate 15 south of Nephi. Garcia-Jauregui engaged in a firefight with four Juab County deputies and was critically wounded; he died the next day of his injuries.
Deputy Utah County Attorney Chris Yannelli said Friday afternoon that the teen made an appearance at a closed juvenile court hearing in Provo that morning. He said the judge granted prosecutors an extension until Feb. 28 to file charges against the teen. She will be kept at a Provo juvenile detention facility until that point, Yannelli said.
"It's possible that charges may arise before that," Yannelli said, adding that prosecutors are unsure whether the girl would be facing felony or misdemeanor charges.
Police believe that Garcia-Jauregui shot and killed Wride after the officer stopped his patrol car to check on the pickup, which had its flashers blinking on State Road 73. Garcia-Jauregui allegedly shot Wride while he was still in his patrol car, then sped south to Santaquin, where he shot 38-year-old Deputy Greg Sherwood in the head.
Utah County Sheriff's Office spokesman Sgt. Spencer Cannon said investigators initially thought a high-powered rifle was used in the shootings, but as of Friday also were considering that a handgun was used, too.
As for Sherwood, he underwent surgery on Wednesday for removal of bullet fragments from his brain, a procedure that was successful, Cannon said.
"The doctors are limiting his visitors, since he had quite a stream of them for a while and they want him to have time to rest and heal," Cannon said Friday. "He's doing as well as can be expected, though. He's communicating and has been up and around and continues to improve."
Tribune reporter Jessica Miller contributed to this story.