Authorities are investigating pictures of Shawn Hornbeck that were apparently taken during the four years the Missouri teen was missing.

The shocking photos appear to show Hornbeck, now 15, inside or near the apartment of Michael Devlin, the 41-year-old man charged with kidnapping him and 13-year-old Ben Ownby. Authorities said they are trying to authenticate the images, but are working under the assumption that the photos are genuine, FOX News affiliate KTVI in St. Louis reported.

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One of the most disturbing of the more than a dozen images obtained by KTVI appears to show Hornbeck with his face shrouded in a red bandana pointing a gun at the camera. Investigators say the images show a "different side" of Hornbeck, and they hope that they will help them piece together the teen's puzzling disappearance.

• Click here to watch the original report from KTVI.

"It's disturbing, but it's not unexpected that there are going to be things revealed from the course of Shawn's captivity that are going to be upsetting to the family," Hornbeck family lawyer Scott Sherman said.

Sherman said the Hornbecks were unaware of the photos until they were contacted by KTVI, but said that the family is prepared to deal with any trauma their son might have experienced during his time in captivity.

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"The family looks at it like this: With what they've been through in the last four and a half years in getting Shawn back, they can deal with anything," Sherman said.

The Hornbecks hope that the photos can be used as evidence to build a case against Devlin, Sherman said. Task force officials say the images are a top priority, but are not sure at this point how important they will be to their ongoing investigation.

Sgt. Al Nothum of the Missouri Highway Patrol said the first thing police want to know is who took the photos.

"We're not just looking at the person in the picture, but obviously you look at everything in the background or the quality of the film or of the digital picture. You look at a lot of things," Nothum said.

Hornbeck was reported missing by his family on Oct. 5, 2002, after he didn't return home from school in Richwoods, Mo. On Jan. 12, 2007, police serving an unrelated warrant at the apartment complex where Devlin lived in Kirkwood, Mo., spotted a white pick-up truck that matched the description of the one reportedly used in the abduction of Ownby four days earlier in Beaufort, Mo. Both boys were discovered inside Devlin's apartment shortly thereafter. Kirkwood is about an hour drive from both Richwoods and Beaufort.

Although he did not attend school during the time he was missing, Hornbeck was apparently allowed to leave the apartment unsupervised while Devlin worked as a manager at a local pizza parlor. He even reportedly attended a local school dance in December with a girl students described as his "girlfriend."

In an interview on "The Oprah Winfrey Show," Hornbeck said he was too "terrified" to try to escape from Devlin's clutches. Many have speculated that the teen is a victim of Stockholm Syndrome, a trauma-induced psychological condition in which a kidnapping victim or hostage develops feelings of loyalty toward his or her captor.

Devlin pleaded not guilt to two counts of kidnapping and one count of armed criminal action, and is being held on $1 million bond. A preliminary hearing is scheduled for March 15.

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