Penobscot County Jail / AP Kyle Dube of Orono, Maine, is shown in a June 2012 photo provided by the Penobscot County Jail via Maine State Police.

BANGOR, Maine -- A man used a fake Facebook account to lure a teenage girl out of her house in an attempt to stage her kidnapping and rescue so he could look like a hero but ended up killing her, a state police affidavit released Wednesday said.

Kyle Dube was indicted Wednesday on charges of murder and kidnapping in the death of 15-year-old Nichole Cable, whose body was found in a wooded area of Old Town this month a week after she went missing.

In an affidavit released after Dube was indicted, Detective Thomas Pickering outlined the scenario leading to the high school sophomore's death. He wrote that Dube told his brother that he used Facebook to trick her into going out of her house in Glenburn, not far from Old Town, while he waited in the woods wearing a ski mask.

When Nichole came along, the 20-year-old Dube jumped out and snatched her, duct-taped her and put her in the back of his father's pickup truck, the affidavit said. Dube later discovered that she was dead, so he dumped her body and covered it with branches, it said.

The affidavit doesn't go into details about how Nichole was duct-taped, and the cause of her death is still being determined by the medical examiner's office.

Dube told his brother that he "intended to kidnap Nichole and hide her; that he would later find her and be the hero," Pickering wrote.

Dube's attorney, Stephen Smith, did not immediately return a phone call left at his office Wednesday evening. He had argued for the affidavit to be withheld, citing threats against Dube in jail, concerns about whether he could get a fair trial and fears for the privacy of his relatives.

Earlier Wednesday, Justice William Anderson had denied a motion by The Associated Press and the Portland Press Herald to unseal the affidavit on First Amendment grounds.

The judge's original order had sealed the affidavit only until Dube was indicted. When the indictment was handed down, the affidavit was made public.

Nichole was reported missing on May 13 by her mother, who said she had left the night before to meet a friend at the end of the driveway but hadn't returned.

Police interviewed a friend of Nichole's named Bryan Butterfield, who said somebody had set up a fake Facebook account in his name and he suspected Dube. Butterfield told detectives that Dube wanted to have sex with Nichole but that she had rejected his advances, the affidavit said.

Investigators determined that Nichole had frequent contact with the fake Butterfield on Facebook and that the person posing as Butterfield repeatedly requested to meet with her before she agreed to meet with him at the end of her road to get some marijuana the night she went missing, the affidavit said.

Police asked Facebook officials to produce records to identify the owner of the fake Butterfield account, which was traced to Dube and his parents' home in Orono.

When a detective interviewed Dube's girlfriend, Sarah Mersinger, she reported that Dube told her where he left Nichole's body. Dube's brother, Dustin Dube, then told police what he knew.

Dozens of law enforcement officers, using aircraft and dogs, and hundreds of civilian volunteers had spent days searching for Nichole, whose body was found on the night of May 20. About 300 people turned out for her funeral.

Canfield reported from Portland, Maine.