Updated

Two different weapons were used to murder a pair of young best friends as they walked along a rural road in Oklahoma, investigators said Wednesday, suggesting two or more people killed the girls.

The detectives based their conclusion from ballistics tests on evidence collected along County Line Road in Weleetka, Okla., where the bodies of Taylor Paschal-Placker, 13, and Skyla Whitaker, 11, were found. The tests showed that two different-caliber guns were used to kill the girls, but it isn't clear whether the guns were handguns or long guns.

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"Where we were looking for one [shooter], possibly two, now it looks more likely there are two or more," Special Agent Ben Rosser of the Oklahoma State Bureau of Investigation said at a press conference Wednesday.

Officials still don't have suspects or an apparent motive in the murder of the girls, killed on Sunday just a few hundred yards from Taylor's home near a bridge she often walked to for exercise.

"This could be some sort of random thrill killing; it could be an attempted abduction," Rosser said. "It could be somebody that just had, for whatever reason, had a personal motive, maybe mistaken identity, or possibly they did interrupt something down near the bridge. We just don't know. But all things are being considered at this point."

An autopsy found the girls had died of multiple gunshot wounds to the chest and face, Chief Investigator Kevin Rowland of the Oklahoma Chief Medical Examiner's office told FOXNews.com.

Rosser wouldn't say Wednesday how many times the girls were shot.

Taylor's grandfather, Peter Placker, found the girls clothed in T-shirts and shorts just 20 to 25 minutes from the time they last were seen. That short window leads investigators to think that the girls were not molested by their assailants, though lab work still is pending.

"As far as a sexual assault, I don't believe they were," Rosser told FOX News.

In addition to the ballistics tests, police were examining shoe and tire prints, shell casings and any computer correspondence the girls made.

The crime scene's isolation leads police to believe locals killed the girls, though Rosser said family members and friends aren't suspected.

This lack of suspects or a motive for the grisly slayings has put this small community of 1,000 on edge and in the national spotlight.

"This just hits to the very core of America," Rosser said. "That two little girls can't go walking down a country lane road in this day and age, it's pretty sad."

Okfuskee County Sheriff Jack Choate is telling parents to keep an eye on their children.

"We don't know what the threat is, but if it were me, I wouldn't let my kids out walking unless there was other people around, you know, that you knew," he said. "Just natural security for your own kids."

Dena Priddy, a teacher's aide at Graham Public School, where Taylor and Skyla were students, has headed the warning.

"I have guns loaded," she told the Associated Press, adding she wouldn't let her teenage daughter out of the house.

The Oklahoma State Bureau of Investigation is offering a $25,000 reward for information leading to the arrest and conviction of the killer or killers. The Bank of Commerce in Weleetka has set up accounts to help raise money for the girls' burials, which are scheduled for Friday.

After a press conference Wednesday, a local chaplain prayed to bring the girls' killers "grief and remorse so strong that they will run no longer, but will come forward and face the consequences of their actions."