Kayleah Wilson's Boyfriend Arrested, but Not for Murder

The 18-year-old is accused of having sex with 12-year-old found dead.

May 22, 2010 — -- Police have arrested the 18-year-old boyfriend of Kayleah Wilson, the 12-year-old whose decomposed body was found Wednesday in Greeley, Colorado, but he is not being charged with murdering the girl who had disappeared nearly two months ago.

Instead, Robert Laurencio Montoya was charged with sexual assault on a child one count of sexual assault on a child as a pattern of abuse, Greeley, Colorado, police said Friday. Montoya was arrested Wednesday, but it was not announced for two days.

"This arrest culminated an investigation that developed from information that probable cause existed to believe the suspect was involved in a sexual relationship with Kayleah Wilson," Greeley police spokesman Sgt. Joe Tymkowych said. "This arrest is separate and distinct from the Kayleah Wilson homicide case that is currently being investigated."

Montoya was being held on $100,000 bond on the two felony charges.

According to ABC News Denver affiliate KMGH-TV, Tymkowych said he could not confirm rumors that Kayleah might have been pregnant. He said police believe the relationship with Kayleah started last fall, when Montoya was 17. The teen turned 18 on Jan. 18.

All court records on the case have been sealed by the Weld District Attorney's Office.

Kayleah Wilson's Body Found 1 Mile From Where She Was Last Seen

The body, found Wednesday just one mile from where Kayleah went missing nearly two months ago, was identified through dental records, said Greeley Police Chief Jerry Garner at a press conference Thursday.

Kayleah Wilson's Boyfriend Arrested for Sexual Assault

"The Weld County Coroner's Office has identified the boy as that of Kayleah Wilson," Garner said. "The information that has been provided says that the death does not appear to be accidental and as a result, a homicide investigation has begun."

The search for Kayleah, who went missing March 28 after leaving her Greeley home to attend a birthday party, has been confounded by an absence of any information or leads, police have said.

"We have not got a suspect," Garner said Friday. "We've got, again this group, this list of people that we're, we're, we're looking at as people of interest in this case."

Kayleah's body was found at 6 a.m. Wednesday by a worker who was inspecting the water levels in an irrigation ditch. Garner said this was an area that had been searched twice by rescue workers when Kayleah first disappeared, and even by search dogs, which never picked up a scent.

Kayleah's family was not at the press conference and, according to Garner, does not want to speak to the media. Garner said that there is nothing to lead investigators to believe that any member of the family "is a suspect in the case."

Police, Mother: Kayleah Did Not Run Away

Kayleah's mother, April Wilson, said that disappearing without calling or coming home was not typical of her daughter.

"She's never run away before," Wilson said after police began to look for Kayleah. "I am worried she may be in danger because none of her friends have seen her, and it is like she just vanished, but that's not possible."

Kayleah, a sixth grader at Brentwood Middle School, was last seen wearing a white-and-pink shirt over a white tank top, blue jeans and white and red shoes. She was described as being 5 feet 1 inch, and approximately 145 pounds with brown eyes and brown hair.

Wilson said her daughter left at 3:40 p.m. for the party, which was just a few blocks away.

Kayleah Wilson's Boyfriend Arrested for Sexual Assault

"She walked over to the couch and said, 'I love you,' and 'I'll be home by 7,' and she walked out the door and that was it," Wilson said. "She had been talking about the party. She was really looking forward to it."

The eight-block area Kayleah would have crossed to get to the party is well-populated and safe, according to authorities.

Wilson also said that she had no concern about letting her daughter walk alone and that the neighborhood is not dangerous.

"We all walk everywhere, we don't even have a car," she said. "It's not a bad neighborhood."

Wilson described her daughter as "loving" and "trusting," and said that she has always been well-behaved.

Other than that, Wilson said her daughter was a typical preteen who had a crush on one of the singers from the folk band Celtic Thunder.

On the morning of the day she disappeared, Wilson said her daughter had gone to church with her and had been happy during a lunch at a local restaurant with her grandmother.

ABC News' Clayton Sandell contributed to this report.