According to Morgan County Coroner Jeff Chunn, Tania Rico died after midnight on Oct. 24 from sharp force trauma to her neck. He says she also had stab wounds to her neck.
Chunn says because Rico was face down, if you walked in the room, you couldn't tell what she died from.
Matias was brought back to the Morgan County Jail from Knoxville on Monday and has a preliminary hearing on Nov. 12 at 9 a.m.
Court documents say a 16-year-old Austin High School student found dead on Oct. 24 had multiple cuts on her throat.
Bernandino Matias, who was found in Knoxville, Tennessee on Oct. 25, is charged in the homicide investigation. Officials say the cuts were caused by a knife or other bladed tool.
According to court documents, Tania Rico's mother found her laying face down in a bedroom in an apartment on Bluebird Lane SW in Decatur. They say her friends had been trying to contact her since about 6:45 a.m. and contacted her mother, who also lives at the address, when they were unable to.
Court documents say during a preliminary investigation, it was found Rico and her live-in boyfriend, Matias, had been together for about three years. Documents say the investigation determined Matias was at the apartment with Rico from approximately 12 a.m. until 4 a.m.
Officials say Matias went to his brother's home around 4 a.m. and asked him to drive him somewhere. They say the brother, Enrique Matias, drove him to Knoxville, Tennessee, and during the ride, Bernandino Matias said he was in a fight with Rico and had knocked or pushed her down on the ground.
According to the court documents, Rico's mother had left the apartment to go to work around 8:50 a.m. and never saw or heard her in the bedroom since the doors were closed. They say she got a phone call at about 10:53 a.m. that Rico was not at school, so she tried to call her.
Court documents say when Bernandino Matias was taken into custody on Oct. 25, he confirmed he was responsible for Rico's death and that he had asked his brother to drive him to Knoxville, Tennessee.