He knocked on her door and asked her to play. She did not make it home.

Kailey Vijil was only 12 years old when she was allegedly lured from her home by a 15-year-old boy in the middle of the night.

The boy allegedly came to Kailey’s family home in Utah just after midnight on Friday morning and persuaded her to come outside with him.

When Kailey asked her relatives if she could play with the teenager, one of them reportedly said yes.

But after about 90 minutes, Kailey’s mum could not find her little girl. She started to desperately search the neighbourhood for her daughter, and eventually alerted police officers at a nearby convenience store to her daughter’s disappearance.

Police followed the signal on the young girl’s mobile phone — and at 3am on Friday, authorities found Kailey’s battered body alone in the middle of an overgrown horse pasture, just four blocks from the girls’ home in Salt Lake City.

Kailey’s body was found with “evidence of trauma”, though police have attested that there was no markings of being shot or stabbed. There were also signs of a struggle at the scene, police said.

“I believe a good-natured child was fooled and unfortunately made a mistake she paid the ultimate price for,” West Valley Police Chief Lee Russo told The Deseret News. “This young girl thought she was helping somebody.”

It appeared that there was no prior relationship between Vijil and the 15-year-old boy, Russo added.

At 1:30pm on Friday, police arrested a local 15-year-old boy who had been recently released from either juvenile detention or a drug treatment facility, according to conflicting local reports. He cannot be identified for legal reasons, as he is a minor.

Police believe Kailey was not the first girl the teenager had targeted that same night. Earlier on Thursday evening, the boy had allegedly asked another neighbourhood girl to come and look at his “fort” in an abandoned house, and yet another girl to help him find a pregnant cat.

Neighbour Stephanie Sala said the same teenager had once asked her five-year-old niece if she wanted to play.

“I had said no because he hadn’t asked for my five-year-old son, my 10-year-old nephew or my 12-year-old son to come and play. He just asked us for the 5-year-old little girl to come and play,” Ms Sala told the Deseret News.

Eight-year-old Mila Montana was also on the list of young girls the teenager had allegedly attempted to prey on: He reportedly tried to lure Mila from her home, but she quickly declined.

“It just scared me, and when I’m scared I’m supposed to go tell my mum. I was in shock because I know about girls being kidnapped and I just want to stay with my family and be happy,” the young girl said.

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A neighbour told 2News of the teenage suspect: “This is the house of a kid that’s had kind of some history in the neighborhood and been in some mischief, to put it politely.”

Neighbour Megan Powell told ABC 4 Utah: “He’s kind of a troublemaker around the neighborhood.”

Police have emphasised that this story must not become a debate about whether Kailey’s parents or relatives should have let her leave her house on the fateful night.

“This isn’t a debate about parenting,” Russo said, “What we are investigating is the death of a 12-year-old girl.”

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A candlelit vigil for Kailey took place yesterday at a local park. Community members lit candles and wore purple, which was the little girl’s favorite colour.

The teen suspect has been booked into the Salt Lake County Juvenile Detention Center for investigation of murder, according to The Deseret News. A judge will now determine whether he will face the charge as a juvenile or as an adult, NYDailyNews reports.

Our thoughts are with Kailey’s family and friends today.

For more news:

SA Police release more images of evidence in bid to identify ‘murdered’ child’s remains.

He reportedly sent her 1400 text messages in a month. And then she died.

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