Classes won't resume until Friday at Danvers High School, where 24-year-old Colleen Ritzer was described as a caring teacher who stood outside her classroom and said hello to even students she didn't teach.
Authorities have not said whether she had any run-ins with Philip Chism, a student new to the school who is charged with murder.
Ritzer was reported missing Tuesday after she did not return home from school. Blood in a second-floor bathroom helped lead investigators to her body, which was dumped in the woods behind the school in a close-knit community about 20 miles north of Boston.
Authorities have not released a cause of death or a motive. Chism, who was also reported missing, was found walking along a state highway overnight.
Fellow students said Chism had moved to Massachusetts from Tennessee before the start of the school year and was a top scorer on the school's junior varsity soccer team.
Jean McCartin, a Danvers School Committee member, said the school has extensive programs to help ease the transition for new students who may have problems, but there was no information about Chism that would have presented any red flags.
"He just presented himself to us like any other student would," she said Thursday. "And that's what I think is so hard for the administration right now. You know, their hearts are breaking because they just didn't know he was in need, if he was in need. We don't know. We just don't know what his motive was, nobody knows at this point. No one knows why he would have behaved in this way and done such a terrible thing."
Students were also puzzled.
"From what I know about him and seeing him every day, it just doesn't add up that he would do such a thing, unless this was all an act to fool somebody," said Ryan Kelleher, 17, who played soccer with Chism.
Chism appeared briefly in court Wednesday for arraignment on a murder charge and was ordered held without bail. His attorney and family declined to comment.
Kyle Cahill, a junior who also plays soccer, said the team wondered where Chism was when he skipped a team dinner Tuesday night.
"We're all just a family. It just amazes me really," Cahill said. "He wasn't violent at all. He was really the opposite of aggressive."The Boston Red Sox held a moment of silence for Ritzer on Wednesday at Fenway Park before Game 1 of the World Series.
Hundreds of people later turned out for a candlelight vigil at the school parking lot, many wearing pink sweatshirts, bows or T-shirts in tribute to Ritzer and her favorite color.
"She supported all of us. We should be there to support her," said Danvers senior Courtney Arnoldy, 18, who had Ritzer for a teacher.
Ritzer lived at home with her 20-year-old brother and her sister, a high school senior.
Her family said they are mourning the death of their "amazing, beautiful daughter and sister."
"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 in a statement provided by her uncle Dale Webster.
Ritzer had a Twitter account where she gave homework assignments, encouraged students and described herself as a "math teacher often too excited about the topics I'm teaching." She was a 2011 magna cum laude graduate of Assumption College in Worcester, a school spokeswoman said. The college will hold a reflection to remember her Friday.
One of her former students, Chris Weimert, 17, said she was a warm, welcoming person who would stand outside her classroom and say hello to students she didn't teach.
"She was the nicest teacher anyone could ever have. She always had a warm smile on her face," he said.
Ritzer is the second teacher allegedly killed by a student in the U.S. this week. A Sparks, Nev., middle school teacher was shot Monday, allegedly by a 12-year-old student.
Associated Press writer Lynne Tuohy in Andover and news researcher Rhonda Shafner in New York City contributed to this report.