FAIRFIELD, IOWA (WHO) – Two 16-year-olds are facing murder charges for their alleged roles in the death of a teacher whose body was found in a public park in Iowa.

Nohema Graber, a 66-year-old Spanish teacher at Fairfield High School, was reported missing on Wednesday. Her body was found later in the day at Chautauqua Park in Fairfield.

Authorities have ruled the case a homicide.

Willard Noble Chaiden Miller and Jeremy Everett Goodale, two 16-year-old students at Fairfield High, are charged with first-degree murder and conspiracy to commit murder for allegedly killing Graber. The two are being prosecuted as adults.

According to the criminal complaint filed with the Jefferson County Sheriff’s Office, authorities found Graber’s body covered with a tarp, a wheelbarrow, and railroad ties in a remote area of Chautauqua Park. Investigators believe she died of trauma to the head.

The criminal complaint also states investigators found social media posts incriminating Miller and Goodale. It states the posts in question showed Goodale knew specific details of the crime and showed Miller’s involvement.

Investigators say those social media posts illustrated why the two may have wanted to kill Graber, how they planned to do it, and their method for covering up the crime.

Graber taught at Fairfield High School for nine years. The Fairfield Community School District canceled classes on Thursday and Friday to give students and teachers a chance to mourn her death.

“We extend our deepest condolences to the family, friends, and loved ones of Mrs. Graber,” said Fairfield Schools Superintendent Dr. Laurie Noll. “At this time, our students’ and staffs’ well-being is our top priority. As a community, we will remain united in this time of tragedy.”