BARRON, Wis. — The crime began with a chance encounter: From the moment Jake Patterson spotted a 13-year-old girl boarding a school bus last fall, he “knew that was the girl he was going to take,” Wisconsin investigators said in court documents released Monday.

In the days that followed, Patterson, 21, mapped out his plot to abduct Jayme Closs, a middle-school student whom he had never met before, the investigators said. He took a shotgun from his father, switched out his car’s license plate and bought a mask from Walmart. He shaved his head and face — to leave no traces — and wiped clean his shotgun shells. He twice drove out to Jayme’s house in the small town of Barron, but saw cars in the driveway or people awake inside, the report says.

Then, late on an October night, Patterson pulled up again to the home of the Closs family — people he had never met — and killed Jayme’s father, James Closs, with a single blast of the shotgun. He then forced his way into a bathroom where Jayme and her mother, Denise, were hiding in a bathtub, the investigators said. He ordered Denise Closs to cover her daughter’s mouth with black tape, then killed Denise. Then he tied up Jayme and forced the teenager into the trunk of his car — all of it in a matter of four minutes.

The details of Jayme’s abduction and captivity, outlined in documents released as Patterson was formally charged in the kidnapping and killings, were elaborately planned, gruesome and terrifying. They told the story of a girl who was forced to spend three months held against her will in the cabin of a volatile stranger after having witnessed the deaths of her parents. It was the situation every parent fears — and one that experts say is exceedingly rare: a targeted attack on a child by a total stranger.

Patterson, who was ordered held on $5 million bail, did not enter a plea during a brief court appearance Monday. Investigators say that he confessed to them and provided the details they described about the planning behind the abduction. Patterson’s lawyers did not immediately respond to messages seeking comment.

Wearing an orange jumpsuit, Patterson appeared via video from the Barron County Jail and answered “no” and “yes, sir” to basic questions from the judge. Patterson, who wears glasses and has close-cropped, receding brown hair, showed no obvious emotion during the court appearance. At various points, he yawned and rubbed his chin.

The allegations have upended Barron, where residents spent weeks searching for Jayme as scores of investigators swarmed to the small town and followed thousands of tips and false sightings. Residents said they were thrilled that Jayme had managed to escape from her captor last week. She has since been staying with family members, who posted a photograph of her smiling and holding her dog, Molly.

But residents were stunned by the investigators’ descriptions of what had happened — the randomness of it, but also the chilling and seemingly intricate planning.

Some parents were newly hesitant about school buses, and wondered aloud what else might no longer be safe.

“I’ll be taking my child to school,” said Amy Christensen, manager of Skippy’s Pub in downtown Barron, a town of about 3,400 people. Since this happened, Christensen said, she has let her 3-year-old daughter sleep with her. “I’ve been holding her close every night,” she said.

The charges against Patterson buck national trends in homicides and kidnappings.

In 2017, fewer than 10 percent of homicide victims were killed by strangers, according to the FBI. And according to the National Center for Missing & Exploited Children, cases in which strangers abduct children are very rare; of more than 25,000 reports of missing children that the group received in 2018, only 77 were abductions by nonfamily members, said Erin Farrell, a center representative.

The prosecution’s 12-page complaint, which included details from interviews by law enforcement officials with Jayme and Patterson, provided chilling answers to questions that had haunted Barron ever since Oct. 15, the night that the Closses were killed and their daughter vanished.

Patterson spotted Jayme last year as he was driving to a job he held briefly at a cheese factory while she boarded a school bus. Within days, authorities said he told them, he was assembling supplies to abduct her and taking steps to disguise his identity. Prosecutors said he resolved to kill anyone else in the Closs home, rather than allow anyone to threaten his plan.

“He indicated that if he had been stopped by police, it was likely he was going to shoot at police officers with the three shotgun shells that he had remaining,” Brian Wright, the Barron County district attorney, said in court.

In fact, Patterson told investigators that he saw police cars speeding toward the Closs home about 20 seconds after he left with Jayme bound and stuffed in the trunk. After slowing down for them, Patterson continued about an hour north to Gordon, where he took Jayme inside a cabin and forced her to change her clothes.

In the 88 days that followed, Jayme told investigators, she was kept inside the cabin and forced to hide under Patterson’s twin-size bed when he had guests over or when he left. Sometimes, she went without food, water or access to a toilet for as long as 12 hours, she said.

Mark Fruehauf, the district attorney in Douglas County, which includes Gordon, said more charges could be filed in the coming weeks related to Patterson’s actions after the initial kidnapping. Fruehauf did not offer details, but court filings said Patterson used force and threats to prevent Jayme from escaping.

When she was forced to hide under the bed, Jayme told detectives, Patterson would box her in with totes and laundry bins that he secured with barbell weights. He would turn on music to prevent guests from hearing any noise she made. And one time, when Patterson believed she had tried to escape, Jayme said he struck her and threatened worse consequences if she tried again.

But last Thursday, after Patterson told Jayme he was leaving for a few hours, she managed to force her way out from under the bed, she said. She grabbed a pair of men’s shoes — apparently Patterson’s — and ran to a nearby road, shoes ill-fitting and on the wrong feet, crying out for help. A woman who was walking by with a dog took her to a nearby home. “I’m Jayme Closs,” the woman recalled the girl saying. “I don’t know where I am.” And then: “Please help — I want to go home.”

Wright, the prosecutor, called Jayme’s escape “incredible.” He said, “You can see the amount of control that he was exerting over her, and at some point she found it within herself at 13 years old to say, ‘I’m going to get myself out.'”

As sheriff’s deputies took Jayme to safety, they set out to look for Patterson. A short time later, deputies saw the car that Jayme had described to them, and pulled him over.

Patterson, who had apparently been out looking for Jayme, told the deputies he knew why they had stopped him.

“I did it,” he said.

This article originally appeared in The New York Times.