Massachusetts authorities on Wednesday charged a 14-year-old high school student in the murder of a math teacher after finding the teacher's body in woods near the school.
The student, Philip Chism, pleaded not guilty to the murder charge and was ordered held without bail in a brief proceeding at Salem District Court, according to the clerk's office.
Chism has been charged as an adult, which could subject him to a longer prison sentence in an adult facility if he is found guilty of killing Colleen Ritzer, 24.
Massachusetts law allows people as young as 14 to be charged as adults when the crime is murder.
Police in Danvers, Massachusetts, began an investigation late on Tuesday after receiving calls that a student at the school and a teacher had not gone home, Essex County District Attorney Jonathan Blodgett told reporters on Wednesday.
After discovering blood in a second-floor bathroom, police extended their search to the woods behind the school, where they found Ritzer's body.
"It was apparent that she was a homicide victim," Blodgett said. "This is a terrible tragedy."
Prosecutors said in court papers that an interview of Chism and surveillance video from the school showed that Chism murdered Ritzer and dumped her body behind the school.
Chism stood quietly, stooping slightly and dressed in a white shirt as he was charged on Wednesday.
Ritzer is the second U.S. educator this week to die in an incident involving a student after a Nevada middle school teacher was shot dead by a 12-year-old student on Monday.
Investigators from the local medical examiner's office on Wednesday carried a stretcher out of the woods where Ritzer's body was found.
Police on Tuesday had issued a missing-child report for Chism, who had recently moved to the area from Tennessee. A photo posted on the Danvers Police Department's Facebook page at the time of the search showed a tall, lanky, short-haired Chism wearing a red and black soccer uniform.
He was found walking along a highway about 12:30 a.m. EDT on Wednesday (0430 GMT).
Students from the school left bouquets of flowers, a teddy bear and a note reading "Rest in peace, Ms. Ritzer, you will be missed" in front of the school.
All public schools in Danvers, which is about 20 miles (32 km) north of Boston, were closed on Wednesday, although police believed there was no continuing threat to public safety.
"We have no reason to believe there were any other suspects involved," Blodgett said. He declined to comment on how Ritzer was killed or if she might have had any type of relationship with the student.
Ritzer's family issued a brief statement to The Salem News asking for privacy.
"At this time we are mourning the tragic death of our amazing daughter and sister," the family said. "Everyone that knew and loved Colleen knew of her passion, her teaching and how she mentored each and every one of her students."
Ritzer described herself as a "Math teacher often too excited about the topics I'm teaching" on her Twitter account, @msritzermath, where she also posted homework assignments and links to math problems.
In the shooting incident in Nevada on Monday, teacher Michael Landsberry, 45, was shot and killed when he tried to stop the 12-year-old student armed with a handgun after he wounded two fellow students, then later turned the gun on himself.
"We will probably never know all the factors that accumulate to unleash this kind of violence, but we must commit to doing all we can to make sure students and educators are safe in our schools," Dennis Van Roekel, president of the National Education Association, a labor union for school teachers, said in reaction to this week's incidents.
(Additional reporting by Daniel Trotta and Brendan O'Brien; Editing by Paul Thomasch, Gunna Dickson and Cynthia Osterman)