A 12-year-old girl was "brutally murdered" in her house after texting her mother to tell her there was someone knocking at the door.
Yhoana Arteaga was found bludgeoned to death in her family's mobile home with her clothing "in disarray", police said.
Detectives believe the killer may have been known to the girl, who was on crutches after being injured roller-skating the previous day, but they have few leads.
There was no evidence of forced entry to the trailer inNashville, Tennessee.
"This is a horrible, brutal thing. I’ve never seen anything this brutal in my entire career," said Sergeant David Kautzman, of Nashville Police Department.
Yhoana was last seen by her mother at 12.30pm on August 10. She was left at home alone and sent a text at 5.30pm saying someone was at the door.
She was found dead when her mother returned home from work with two of her other children at 6.45pm.
The girl had suffered blunt force trauma to her body, police spokesman Don Aaron told a press conference. She had not been shot or stabbed.
Despite police appeals investigators said they have "very limited" information to follow up, reported news channelWKRN.
“She was brutally murdered, and if anyone has any information whatsoever that could help in this investigation, please contact us,” Mr Aaron said.
"We believe there are persons in this community who have knowledge of a person who may be responsible for this.
"Please, for the family’s sake, for the sake of this 12-year-old deceased girl, let us know."
He said the absence of signs of forced entry "would seem to indicate she would know the person responsible".
"We haven’t confirmed that yet, but it’s a good possibility,” the spokesman added.
Officers have been questioning neighbours about any suspicious activity in the area. A detective said police had some persons of interest but declined to elaborate.
Yhoana's school, Liberty Collegiate Academy, paid tribute to the "treasured" seventh-grade pupil.
"Our hearts are broken as we mourn the loss," the school said on Facebook.
"Our thoughts are with Yhoana’s family during this incredibly difficult time. Grief counsellors will be on site at Liberty next week to support teachers and students. We love you, Yhoana."