(CNN) -- Whenever Colleen Allen called, she knew her adopted daughter Angela would come home -- with a slight delay to be expected, because folks in their western Arkansas neighborhood inevitably wanted to talk to the teenager with the big heart.
"It'd take her maybe 10 or 15 minutes because she'd always have to stop to visit Mom No. 25 or Mom No. 5, because all of these other parents adopted her just like she was a member of their family," Colleen Allen, who is also the girl's biological grandmother, told HLN's Nancy Grace on Friday.
But just over three hours after Allen tried to reach her on her cell phone the night of February 10, 16-year-old Angela still wasn't back from her "walk around the block -- which she had done hundreds of times." And when she woke up Saturday morning, Angela's bed hadn't been touched.
"I said, 'Oh my god, something's happened,'" Allen said.
Her nightmare came true more than a week later, when cadaver dogs detected the presence of human remains on property belonging to the brother of Lloyd Jones, a 36-year-old convicted rapist, according to an arrest affidavit.
Investigators dug up a "large, blue, plastic barrel," in which sheriff's deputies soon noticed a "human hand and a pair of shoes through a hole," the affidavit stated. Days later, the body inside was identified as Angela Allen's.
On Wednesday, Jones pleaded not guilty to first-degree murder in the girl's death.
His court-appointed lawyer, Rita Watkins, confirmed that he is being held on $1 million cash bond. She said Thursday that while she'd met with Jones, they hadn't discussed the case yet.
Authorities, however, have laid out what they claim Jones said in the arrest affidavit.
Jones came to investigators' attention after they learned he and Angela Allen met each other over mBuzzy, a social network that helps "users to instantly locate and IM with new friends using your wireless devices location," as described on the service's website. The pair also had exchanged text messages, according to the affidavit.
After being read his Miranda rights, Jones admitted to picking up Angela in her hometown of Van Buren, Arkansas, and "making out" with her by the Arkansas River, according to the arrest affidavit.
When he learned the girl was 16, Jones told police "he violently pushed her into the water and left her there."
Investigators pressed on, getting consent from Jones' brother to search his property outside Lavaca where he was building a shack.
The affidavit also details a February 19 meeting between Jones and his father at the Sebastian County Detention Center. In a recording of the meeting, Jones is heard saying, "I panicked -- I did it."
Two days later, an autopsy revealed that Angela died after being strangled, with evidence of trauma around her throat and no fluid left in her lungs, said the affidavit.
According to court documents, Jones was arrested in December 2000 on rape charges and convicted less than six months later.
What comes next for Jones is secondary for Colleen Allen. She's still struggling to come to grips with the idea that Angela's dreams of becoming a registered nurse will never be realized.
Nor is it easy to understand how a girl who brought so many smiles to others and "just loved life" could have her own extinguished so suddenly.
"Angela was a fun-loving child, she was trusting, she loved children, she loved her school, she loved her church," Colleen Allen recalled. "She would find the most simplest thing (and) take the simplest joy out of it."
HLN's Natisha Lance contributed to this report.