Philip Chism, a 14-year-old student has been charged with the murder of a 24-year-old Massachusetts math teacher, Colleen Ritzer, earlier this week.
Blood found in a second-floor school bathroom helped lead investigators to the body of Ritzer, who was allegedly dragged into the woods by Chism.
Chism was arraigned on a murder charge Wednesday and held without bail.
The Danvers, Mass., teenager, described by classmates as soft-spoken and pleasant, was found in a nearby town after he did not return home on Tuesday.
"We have no reason to believe that any other suspects are involved," Essex County D.A. Jonathan Blodgett said told reporters during a news conference.
Officials didn't release a cause of death and haven't discussed a motive in the Massachusetts teacher's killing. It is believed that he stabbed her to death.
A court filing said that Ritzer and Chism were known to each other from the high school, but it did not elaborate on the relationship between the two.
The arrest was made based on statements by the suspect and corroborating evidence at multiple scenes, area investigators said in court documents.
Ritzer's family said they are mourning the death of their "amazing, beautiful daughter and sister," who was beloved by her Danvers students as well.
"Everyone that knew and loved Colleen knew of her passion for teaching and how she mentored each and every one of her students," the family said.
At his arraignment in adult court, Chism's defense attorney, Denise Regan, argued for the proceeding to be closed and her client to be allowed to stay hidden.
The judge denied the request to keep his identity anonymous but granted Regan's request for the teenager to be given a mental-health evaluation.
A not-guilty plea was entered on Chism's behalf.
The tall, lanky teenager had moved to Massachusetts from Tennessee before the school year and was a top scorer on the school's junior varsity soccer team.