Police have refused to reveal Yhoana's exact cause of death but have stated the youngster was repeatedly bludgeoned.
"An examination of the crime scene, as well as autopsy results, show that Yhoana was, frankly, brutally murdered," Metro Nashville Police Department (MNPD) spokesman Don Aaron told the Tennessean. "Without being overly specific, it was blunt force trauma to her body. Her clothing was in disarray."
Investigators won't say if Yhoana was sexually assaulted, or whether they believe the family's home was robbed.
The girl's chilling final text message, sent at around 5.30pm, is being treated as a crucial clue in a case with very few leads.
The knock on the door, combined with no sign of forced entry, has led police to believe Yhoana was familiar with the person who killed her.
"We do believe the victim knew her assailant," said Metro Nashville Police Lt. William Mackall, who is overseeing the case.
Aaron said that while detectives were pursuing "a few leads" and identified some "persons of interest," they had been disappointed by the low number of tips to CrimeStoppers considering the nature of the crime.
Of the "handful" of calls received, many had proven to be "left field" time-wasters. In contrast, people who really did have information on the case had not called in.
"We believe there are persons in this community who have knowledge of a person who may be responsible for this," Aaron said.
"Perhaps the person responsible has spoken to others, has bragged. If that's the case, please, for the family's sake, for the sake of this 12-year-old deceased girl, let us know so we can take that information and move further."
Police have also delivered a message to media in Spanish in an effort to reach a wider local audience of potential tipsters.
With so few witnesses coming forward, investigators are hoping a breakthrough will come in the form of forensic evidence.
"Detectives are optimistic that a meaningful lead or leads will result from scientific testing being conducted by the MNPD Crime Laboratory," police said in a statement issued over the weekend.
"This case is a priority for police department scientists as well as fingerprint experts who are studying a number of fingerprints discovered during the processing of the residence."
Detectives have also been grilling Yhoana's friends and classmates for possible clues about who could have murdered her and why.
Yhoana was a popular student at Liberty Collegiate Academy in Nashville. The school posted a moving tribute to the 7th grader on Facebook last week, calling her a "treasured member" and posting a photograph of the child, using a computer, that has become the face of the tragic case.
Yhoana's mother told police she last saw her child at 12.30pm on August 10 when she came home to share lunch with her before returning to work at a dry-cleaning business.
Their next contact was at 5.30pm when she received Yhoana's text message about somebody knocking at the door. At 6.45pm, Yhoana's mother, 14-year-old sister and 10-year-old brother arrived home to find her dead.
One of the family's neighbours at Hillview Acres Mobile Home Park, Sheila Gentry, described the dead girl as "happy all the time" and "always polite".
"This is a quiet trailer park," Gentry told reporters last week.
"We all try to keep an eye out for each other."
Park manager Anthony Hinton told how Yhoana would always wave to him from inside her family's car as they drove past his office.
"She seemed like she was going to be a stand-up person, just from the kindness she always showed," he told the Tennessean.
