Austin Reed Sigg
© AP/Westminster Police DepartmentThis booking photo released by the Westminster, Colo., Police Department shows Austin Reed Sigg.
Westminster - A teenager who lived just a mile from a 10-year-old Colorado girl who was abducted and killed earlier this month has been arrested in her death, along with a May attack on a runner, authorities said Wednesday.

Police in the Denver suburb of Westminster said they took 17-year-old Austin Reed Sigg into custody on Tuesday night after receiving a phone call, apparently from his mother, that led them to Sigg. He was formally arrested Wednesday.

Reached by phone, Sigg's mother told The Associated Press he turned himself in.

"I made the phone call, and he turned himself in. That's all I have to say," said Mindy Sigg, before she broke down in tears and hung up.

Police announced the arrest as agents searched the home of Sigg, an Arapahoe Community College student described by former classmates as a smart "goth kid" who was interested in mortuary science.

Authorities declined to elaborate on the arrest and have released few details about the case. Court documents have been sealed, but a police custody report said Sigg was cooperative when he was arrested and waived his rights.

Jessica Ridgeway disappeared Oct. 5 while walking to school. Her remains were found five days later in a field at a park, and police said her body was "not intact."

The arrest came a day after police said Jessica's abduction was connected to the May 28 attempted kidnapping of a 22-year-old runner at another area park, the Ketner Lake Open Space.

In that case, a woman fought off a stranger who grabbed her from behind and put a rag that smelled of chemicals over her mouth, authorities said. Westminster investigator Trevor Materasso said Tuesday police hadn't been able to determine if the substance on the rag was meant to subdue the woman.

Authorities didn't say why they believe the two crimes are linked, but they noted Sigg will be charged in both. His first court appearance is set for 8 a.m. Thursday.

Sigg attended Witt Elementary - the same school Jessica went to - but he moved on to middle school in 2007, before she enrolled at Witt, Jefferson County Public Schools spokeswoman Lynn Setzer said.

Jessica was on her way to Witt when she disappeared.

Sigg later attended Standley Lake High School while also taking classes at Warren Tech, a district school that offers specialized training in health science, public safety, technology and other fields.

He left the school district in July after finishing the 11th grade and later earned a GED. School officials don't know why he left.

Arapahoe Community College officials confirmed Sigg is enrolled there but wouldn't release other details.

As technicians in white coveralls searched Sigg's home, former high school classmates painted a picture of Sigg as an intelligent teen who often wore black and complained about school but who would stay late sometimes to work on computers.

Sigg was interested in mortuary science and was taking forensics classes, said Rachel Bradley, 17, who attended Standley Lake with him. Arapahoe Community College offers the state's only accredited mortuary science program.

"It's just so weird to grasp the concept of how, like, I knew him and how he lives so close to us," Bradley said.

"I never saw it coming," Bradley said of the allegations against Sigg.

Yearbooks showed Sigg was a member of the choir in his freshman and sophomore years.

Dakota Foster graduated from Standley Lake in 2011, a year before Sigg left. Foster said he and his friends sat at the opposite end of a cafeteria table from Sigg and his friends.

"He was really nice and laughed a lot with us and told jokes, and laughed at our jokes," Foster said.

Foster, 19, said he didn't know Sigg well, but "he used to hang out with a lot of us in what we called the goth corner (of the school cafeteria), where all the metal heads were."

"He wore all black so he fit it," Foster said. He added he wasn't surprised that Sigg left high school after the 11th grade.

"I know he didn't like his classes very much," Foster said. "He always complained about school."

Neighbor Brooke Olds, 13, said she usually saw Sigg alone on a skateboard or scooter.

"He was shy and kept to himself," she said.

Police said they notified the Ridgeway family of the arrest Wednesday morning. Jessica lived in Westminster with her mother, Sarah Ridgeway. Jessica's father, Jeremiah Bryant, lives in Missouri.

"We hope and pray that this arrest brings them some measure of closure in dealing with this enormous loss that they've suffered," Westminster Police Chief Lee Birk said.

Jessica's great-grandmother Donna Moss told Kansas City-area reporters that she feels for Sigg's mother but has to fight the rage she has toward Sigg because she knows as a Christian she should forgive.

"I think it's all I've got within me to not want to just burn him, and I mean burn him," she said.

The arrest brought some relief to the community, which has been on edge as authorities searched for Jessica's killer. More parents have been waiting with their children at bus stops, and high school students have volunteered to walk younger children to school to keep them safe.

"Every parent in every Colorado community will rest a little easier tonight," said Gov. John Hickenlooper, who has a 10-year-old son. "While we still mourn the death of Jessica Ridgeway, we are relieved an arrest has been made and the pursuit of justice can continue."

Numerous people have paid their respects to Jessica at a memorial to her at a park near her home. It has been decorated with flowers, balloons and stuffed animals.

Jessica was walking down a quiet street in her modest neighborhood when she was last seen alive. Her school backpack was found three days later in Superior, another Denver suburb about seven miles northwest of her home.

After Jessica's disappearance, more than 1,000 officers and 10 agencies, including the FBI, investigated the case, following up on more than 4,000 leads.

Authorities had long said Jessica's killer could be someone from the community. They asked residents to be on the lookout for anything suspicious from their bosses, friends and family members, watching for things like leaving home unexpectedly, missing appointments or changing their appearance.