Abducted teen Shawn Hornbeck was ordered to stand guard over another snatched boy, Ben Ownby, and hide him from police after they were left alone time and time again in their captor's apartment, an official close to the investigation told The Associated Press.

Meanwhile, authorities are investigating pictures of Shawn that were apparently taken during the four years he was missing.

The shocking photos appear to show Hornbeck, now 15, inside or near accused kidnapper Michael Devlin's apartment. 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.

• Click here to watch the original report from KTVI.

Authorities on Thursday announced that a task force comprised of FBI, Highway Patrol and local police has been formed to investigate whether Devlin has any connection to any unsolved cases of missing children in the region.

The Associated Press reported that Shawn's cooperation with accused Devlin was the result of what Shawn experienced during his first 30 days of captivity after Devlin allegedly kidnapped the boy in 2002 when he was just 11 years old.

Police have not said whether they think Devlin sexually abused the Missouri teen during his time in captivity, but Shawn's parents have said they believe he endured some form of abuse.

The official told The Associated Press that Shawn's isolation and abuse during that first month were so intense that his identity was torn apart. Over time, Shawn began to see Devlin as his protector and surrogate parent in a pattern common to many abuse victims, the official said.

The source would not elaborate on what happened to Shawn during the 30 days, but said details of the abuse and captivity would emerge soon when they are used as evidence against Devlin. The 41-year-old pizzeria manager is charged with kidnapping Shawn and Ownby in separate remote Missouri towns four years apart.

Shawn was kidnapped near his home in Richwoods, while Ben was abducted in Beaufort on Jan. 8, and a white pickup seen speeding away led police to Devlin.

The official told The Associated Press that Shawn answered the door the evening of Jan. 11 when authorities arrived to question Devlin. Before Shawn answered the door, he and Devlin told Ben to hide behind the door of Devlin's bedroom and to remain silent. Shawn spoke with the authorities, as did Devlin.

Devlin refused to let authorities enter his home, and officers did not have probable cause at the time to force their entry. The next day, officers raided the home and found the boys.

The official told The Associated Press a previous news report claiming Shawn helped Devlin kidnap Ben was largely inaccurate. That story and other bits of information have painted a skewed picture of a young boy who was forced against his will to live with Devlin for years, the official said.

"Until you understand what he went through, don't be looking at these little snippets and judging" Shawn, the official said. "He's a victim. He was kidnapped. He was taken from his parents. He was forced to live with this guy. He was forced to accommodate."

'Disturbing' Photos Found in Devlin's Apartment

On the photograph aspect of the investigation, 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 see the photos

"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.

"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.

Click here to see Devlin's Hornbeck kidnapping charges.

Click here to see Devlin's Ownby kidnapping charges.

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The Associated Press contributed to this report.