Authorities said charges will be filed against Sigg for the May 28 attempted abduction of an adult jogger near Ketner Lake, which authorities confirmed earlier this week was connected to Jessica's kidnapping and murder.
Sigg will be charged with two counts of murder in the first degree and a second-degree kidnapping charge, among others. He will make his first court appearance Thursday at 10 a.m. in Jefferson County.
"Every parent in every Colorado community will rest a little easier tonight," Gov. John Hickenlooper said in a news release. "While we still mourn the death of Jessica Ridgeway, we are relieved an arrest has been made and the pursuit of justice can continue. We are especially grateful today to law enforcement officers at all levels for their quick action in this case."
According to police documents, Sigg is a student at Arapahoe Community College. On March 23, he won second place in the Crime Scene Investigation division of the Health Occupation Students of America State Leadership Conference competition.
According to arrest documents, Sigg lives about a block west of Ketner Lake Open Space and about 1½ miles south of where Jessica Ridgeway was snatched from the street as she walked to school the morning of Oct. 5.
Police are blocking access to Sigg's home. A search warrant is being served on the home, Westminster police investigator Trevor Materasso said.
Austin Caisse, 17, is a student at Standley Lake High School and said Sigg used to attend there.
Caisse has known Sigg since elementary school, although he said they have been out of touch the last year.
When Caisse heard the news of Sigg's arrest, he said he thought, "God, don't let it be him," then "Why?"
Caisse said Sigg "was always egotistical, but I never thought he would go this far." He added, "I'd expect him to get into a fight before leaving high school not murder someone."
He said Sigg was really into Japanese culture like anime, and liked to play computer games. The two shared an interest in collecting knives.
"We got into a lot of verbal fights," Caisse recalled.
He remembered that Sigg had a girlfriend for awhile and thought he was "really nice to her and treated her well." He described Sigg's family as "awesome" and said they said they were very generous with Sigg, whom he described as "brilliant."
Investigators are examining the contents of what looks like a construction trash bin across the street from Sigg's home.
On Monday, police confirmed a link between Jessica's disappearance and the attempted abduction of an adult jogger on Memorial Day near Ketner Lake. That woman told authorities that a man attempted to cover her face with a chemical-soaked rag.
The woman said she initially jogged past the man before he grabbed her from behind, "trying to put a rag over her mouth. She said the rag had a chemical smell on it. She was able to get away and call 911 from her cellphone," police documents say.
The woman described the man as white or light-skinned and between 18 and 30 years old, with brown hair and a medium build. He was about 5 feet 8 inches tall.
Jessica disappeared after she left her Westminster home to walk to school. Her body was found "not intact" 11 miles away in an Arvada open space on Oct. 9.
Staff writers Yesenia Robles and Ryan Parker contributed to this report.