ALEXANDRIA, Minn. -- Police say a missing western Minnesota teen is safe after being held against her will for four weeks and swimming across a lake to escape her captors.
The 15-year-old girl had been missing since Aug. 8, when she was last seen at her mother's home in Alexandria, Minnesota. Alexandria police say three men are in custody, accused of kidnapping, physically and sexually assaulting the girl and threatening her with weapons.
CBS News generally does not name victims of sexual assault and is not naming the girl.
"After 29 harrowing days, [the girl] is safe and has been reunited with her family," Alexandria police chief Rick Wyffels said at a Wednesday press conference.
He described her as "an unbelievable young woman" with "a lot of strength."
The disappearance had been widely publicized on local news outlets and on social media, and a $7,000 reward had been offered for information, reports the Minneapolis Star Tribune.
Formal charges are pending for the three suspects, Thomas Barker, 32, Joshua Holby, 31, and Steven Powers, 20. Wyffels said Wednesday that Barker was an acquaintance of the teen, and that he "tricked" her last month by asking for her help with a family situation. He said the teen got into Barker's car and Barker drove her to the home in Carlos he shared with Holby.
"Once inside, that's where [the girl's] nightmare began," Wyffels said.
He said the roommates and later, their friend Powers, "repeatedly assaulted" the girl over the course of weeks. He said Powers came to visit the home about a week after the girl's abduction and "became a part of it."
Wyffels said the girl was tied up with zip ties during portions of the captivity and eventually moved from Barker's home to various other locations including a cornfield, and then to a foreclosed property in Grant County. There, Wyffels said, she was held in a "secure area" towards the back of the home where she wasn't able to escape, at times in a closet.
He said the girl was fed fast food, but he wasn't sure how regularly.
On Tuesday, the men left her alone to get food -- the first time she had been left alone in 29 days, according to Wyffels -- and that's when she made her escape.
"She bravely ran from door to door nearby, trying to find someone to help," she said. "Eventually she swam across a portion of Thompson Lake, and that's when she located a man and asked him to call 911."
Wyffels said the farmer who located the teen immediately recognized her because her missing person case had been so widely shared in the community.
"He was able to name her before she was even able to say any words because he knew exactly what the story was all about," Wyffels said.
The farmer, who didn't want to be named, told CBS Minnesota station WCCO-TV he at first noticed what he thought was a deer in grasslands near his property. He got in his pickup truck and started driving towards it, and that's when he saw the teen come running toward him.
"When she came running out of the grass I thought, 'Oh my gosh, you've got to be kidding," the man told the station. "It was a great feeling -- 'Get in the pickup, we're going to help you now.'"
Wyffels said the farmer drove the teen to the nearby community of Elbow Lake, and that's when the teen pointed out one of her captor's vehicles. A deputy was able to track down the driver, Powell, and arrested him.
Barker and Holby were arrested later in Glenwood after a state trooper spotted their car.
Wyffels said "no one has stated why they targeted her specifically" and he couldn't speak to a motive.
"Why does a human being do this? There's no explanation," Wyffels said.
He cautioned that they believe the version of events to be true, but that the investigation is ongoing and "everything is subject to be different once the final story is told."
Wyffels praised the girl's mother and family, who he called "amazing people" and said they never gave up the search for their daughter. A photo posted on social media shows the girl, wrapped in a blanket and with wet hair, smiling next to her mother.
"There's nothing more reassuring in my career path of 34 years when you have the opportunity to watch a young daughter and her mother reunite," Wyffels said. "It's the best part of this story. It's a happy ending."