Sources: Teen followed Danvers teacher into bathroom, killed her with box cutter

Danvers, Massachusetts (CNN) -- There is a spot in the halls of Danvers High School that will always remind students and teachers of Colleen Ritzer. The bathroom, where the math teacher was killed on Tuesday.

The school will open its doors to high school students again on Friday, but the bathroom will remain closed, police said. It is still an active crime scene.

How was Ritzer killed? With a box cutter the suspect, 14-year-old Philip Chism, had brought into school, a source close to the investigation says.

What happened to her body afterward? It was stashed in a recycling bin, rolled outside, then dumped about 20 feet into woods behind the northeastern Massachusetts high school's athletic fields, adds another source. It was left there -- not buried, not even covered.

And where did the alleged killer go afterward? After changing his clothes, he went to a Wendy's fast food restaurant and a movie, sources say, before police in a neighboring town saw him walking on a busy road under the pitch-dark sky early Wednesday.

Those are the answers, many of them revealed Thursday, two days after the teacher's killing. Yet the question of why this happened -- why a popular young educator who always wore a smile and went the extra mile was killed allegedly by a teenager who friends, family and co-workers described as reserved and well-behaved -- continues to loom large.

Teen charged with death of math teacher Sources: Teacher killed with box cutter Students remember 'great' teacher Friend remembers slain teacher

Chism, who had moved to the Boston suburb of Danvers before the start of the school year, remained jailed without bond Thursday. A grand jury will play a big part in deciding his next step: If they indict him for first- or second-degree murder, he -- like any juvenile age 14 or older -- would be tried as an adult, based on Massachusetts law.

Meanwhile, the tight-knit North Shore community is still trying to make sense of what he allegedly did and of life without a teacher who so many appreciated, learned from and loved.

'It's just surreal how quickly someone can go, and how much we take for granted every day,' said Danvers High student Chris Weimert. '(Ritzer was) the nicest teacher you could ever have. I can't believe it.'

Two missing persons' reports come together

Students and colleagues described the 24-year-old Ritzer as someone who gave everything for her students -- be it a pat on the back, a sensible explanation to a tricky concept, or the time, effort and heart to work through problems, math or otherwise, with them.

One of those students was Chism, a freshman.

He'd been doodling and listening to music during his Algebra I class in the school's final period, classmate Cambria Cloutier told CNN. Creating such drawings was unusual for Chism, who Cloutier recalled rarely participated in class discussions but was 'a really good student.'

When the final bell sounded at 1:55 p.m. Tuesday, Ritzer asked him to stay after class, according to Cloutier, who sat two desks over from Chism.

While shuttling between two afterschool meetings, Cloutier said she looked into the same classroom and saw Ritzer standing by her computer and Chism sitting in a chair about five to 10 feet away. The teacher smiled at her, Cloutier recalled.

At some point that afternoon, Ritzer went to a regular students' girls bathroom on Danver High's second floor, as someone was in the locked faculty bathroom, a source close to the investigation said.

Chism allegedly followed her in.

There, Ritzer was punched a few times before being killed with a box cutter around 3:30 p.m., said a source.

Her body went into a recycling bin, then outside the school where it was tossed. Authorities eventually found a bin that apparently had been thrown off an embankment some 100 feet away from Ritzer's body, a source said.

Before police found her -- before they even knew she was missing -- they'd started looking for Chism.

This was in the early evening, with Danvers Police tweeting to residents that he hadn't returned home and was last seen around the Hollywood Hits movie theater in the town some 20 miles northeast of Boston.

While they were looking for him, police got a call around 11:20 p.m. Tuesday about another missing person: Ritzer. She wasn't home either, nor had she answered her phones.

Read the complaintA quiet and normal student

The stories started coming together about an hour later, when police officers in nearby Topsfield found Chism walking along Route 1.

Whatever he told detectives in his subsequent interviews, whatever they saw in surveillance footage from the school, led to Chism's arrest for murder. It also led them to Ritzer's body in the woods.

Chism is a quiet young man, those who know him said. He excelled at soccer and made a harmless impression.

'He ... seemed quiet and reserved, but he just seemed normal,' said Ariana Edwards, who was in Chism's English class.

Chism didn't drink or do drugs, and he came from a good family, one of his closest friends said. He described Chism as a good athlete who was shy at first but eventually warmed up to people, adding that he hadn't been acting strangely lately.

A teacher who went the extra mile

Friends got their first hint that something was awry when Chism didn't show up for soccer practice Tuesday. The team set out to look for him after seeing texts that he was missing.

He was a newcomer to Danvers, a town of about 26,000 people. His family had bounced around, and he had lived in different cities in Tennessee and Florida since he was in fourth grade, authorities in those states said.

Meanwhile, many were at a loss in Danvers to explain the death of Ritzer -- a woman who inspired many, whether it be in the classroom or online, with her heart, intellect and positive spirit.

'She was talking on Saturday about this year was a good year. She was teaching freshmen for the first time. She was happy,' said Jen Berger, Ritzer's best friend. 'I don't even know what the world is like without her. It's a scary thought.'

Sympathy spread through the region, making its way into the baseball World Series. Bleachers full of fans who had assembled to watch the Boston Red Sox take on the St. Louis Cardinals observed a moment of silence in Ritzer's honor before Game 1 began Wednesday night at Boston's Fenway Park.

Ritzer, a 2011 graduate of Assumption College who was working towards a master's degree at Salem State University, seemed to always wear a wide smile and was approachable to students and colleagues alike, said Charlotte Dzerkacz, who became good friends with Ritzer in 2011 when they taught at the same middle school.

'She was energetic, she was compassionate,' Dzerkacz said. 'You couldn't ask for anything more from a teacher or a friend.'

Salem State issued a statement lamenting Ritzer's death.

'She believed children have much to offer and often do not realize how special they are as individuals,' the university said. 'In her application to Salem State she said she was dedicated to 'helping students in times of need.''

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Ritzer was known to take to Twitter to dole out homework assignments and wisdom to her students.

'No matter what happens in life, be good to people,' she wrote in August. 'Being good to people is a wonderful legacy to leave behind.'

CNN's Pamela Brown and Don Lemon reported from Danvers, while CNN's Greg Botelho wrote and reported from Atlanta. CNN's Lateef Mungin, Kevin Conlon, Dana Garrett, Laurie Segall, Eden Pontz, Rob Frehse, Rose Arce, Chandler Friedman, Stephanie Gallman, Alexis Weiss and Bob Crowley, as well as journalist Alexandra Field, contributed to this report.