Sources knowledgeable about the investigation said Philip Chism brought the box cutter to school with him and changed his clothes after he allegedly killed Danvers High School math teacher Colleen Ritzer, CNN said.
The source said Chism killed Ritzer in a school bathroom the removed her body from the school in a recycling bin and dumped it in nearby woods.
Chism was charged Wednesday as an adult in Ritzer's death and was ordered held without bail. He pleaded not guilty.
Between the time of Ritzer's death and Chism's capture, the suspect went to watch Woody Allen's movie, "Blue Jasmine," ABC News reported.
The ordeal started Tuesday as a missing person case for both Chism and Ritzer, CNN said. Authorities first searched for Chism after he was reported missing early Tuesday evening, and later received word that 24-year-old Ritzer also was missing.
Police in Topsfield, just north of Danvers, spotted Chism walking along a busy road about 12:30 a.m. Wednesday, Essex County District Attorney Jonathan Blodgett said.
At the high school, police found blood in a second-floor bathroom, Blodgett said. The teacher's body was found behind the school.
After questioning Chism and reviewing the school's surveillance video, detectives placed the teen under arrest.
Investigators said Chism killed Ritzer Tuesday afternoon in the school's faculty bathroom, ABC News said.
In court Wednesday, it was alleged the teenager "did assault and beat" Ritzer, leading to her death," CNN said.
"The juvenile was subsequently placed into custody and booked for murder," a criminal complaint said.
Blodgett did not offer specifics on the relationship between Chism and Ritzer, although is office said the teen was in one of her classes.
Authorities also have not offered a possible motive.
A prayer vigil was conducted Wednesday in Danvers outside the high school where hundreds of students and community residents remembered Ritzer as a respected, dedicated teacher, ABC News said.
A moment of silence for Ritzer was held before Game 1 of the World Series between the Boston Red Sox and the St. Louis Cardinals.
Chism's next court appearance is Nov. 22 for a probable cause hearing.
On Monday, a Sparks, Nev., middle school teacher was allegedly shot by a 12-year-old student.
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