"He fit right in like a normal, everyday person," Przybycien said Friday, noting that teen paid cash for his ticket and had on clean clothes.
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.
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.
A quiet and normal student
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.
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.
Friends, relatives bewildered by arrest of 'storybook kid' in teacher slaying
A teacher who went the extra mile
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 toward 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.' "
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."