Image source, Police handoutImage caption, Nohema Graber, 66, was prominent in the Spanish-speaking community
Two Iowa teenagers have been charged with murdering a local Spanish teacher after police discovered incriminating social media posts.
Nohema Graber, 66, was found dead in a park in the city of Fairfield, several hours after being reported missing, authorities said.
Police say the suspects posted details of the killing, efforts to hide it and a possible motive to social media.
The teenagers, both 16, will be tried as adults for the murder.
According to court documents, Ms Graber had been reported missing on Wednesday morning.
Police later discovered her body at Chautauqua Park in Fairfield, a city of just over 9,000 people located 150km (95 miles) from the state capital, Des Moines. She had been known to frequent the park.
Early investigations suggested she had suffered "trauma to the head", the documents show. Ms Graber's body was found hidden under a tarpaulin, wheelbarrow and railway sleepers.
Authorities say a tip led them to social media exchanges and posts which showed that the two teenagers, Willard Noble Chaiden Miller and Jeremy Everett Goodale, had "specific details" about Ms Graber's disappearance and murder.
"The details included, but were not limited to, the motive for killing Graber, the planning and execution of the means to kill Graber, as well as deliberate attempts to conceal the crime," according to the criminal complaints against the teenagers.
Investigators later searched the teenagers' homes and collected items of clothing, some of which appeared to have blood traces.
A witness also told police he had seen the teenagers in the park the day before Ms Graber was reported missing.
When interviewed by investigators, Willard Miller admitted to being in the park as the murder took place, as well as "providing materials" used in the murder and in trying to help conceal it.
No details about a possible motive have so far been released.
Ms Graber, a Mexican-born Spanish teacher, had been employed at Fairfield High School since 2012, the school district's website shows. Both the teenagers were students there.
In a statement, Iowa Governor Kim Reynolds said that Ms Graber "touched countless children's lives through her work as an educator across our state by sharing her passion of foreign language".
"I am confident through the work of our dedicated law enforcement that justice will prevail," Governor Reynolds added.
The school's students were dismissed early on Thursday and classes were cancelled on Friday. A vigil was planned for Friday night.
Preliminary hearings for the two accused are scheduled for 12 November, KCCI, a local CBS-affiliate, reported.
Iowa law allows cases of juveniles from the age of 14 to be transferred to adult courts.