She was a 2011 graduate of Assumption College in Worcester, a school spokeswoman said Wednesday. She graduated magna cum laude with a bachelor of arts degree in math, a minor in psychology and a secondary education concentration, according to the college's 2011 commencement program.

Chris Weimert, 17, was a student in Ritzer's geometry class last year. He said she had taught at the school for two years and 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.

Weimert said the suspect, who he knew from seeing him around school, "seemed like a good kid." He said, "It really threw the whole town of Danvers a curve ball."

Kyle Cahill, a junior, said he knows Chism from the soccer team. He said the 14-year-old moved to Massachusetts from Tennessee before the school year began and was a top goal scorer on the school's junior varsity team.

He called him a quiet, nice kid.

"He wasn't violent at all. He was really the opposite of aggressive," Cahill said.

Cahill said there was a soccer team dinner Tuesday night that the accused teen skipped, and team members were wondering where he was.

"We're all just a family. It just amazes me really," he said. "I'm just stunned."

Ryan Kelleher, a senior who also plays soccer, said the arrest of the soft-spoken Chism didn't make sense to him.

"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," the 17-year-old said.

Kelleher took Ritzer's algebra class last year and said hello to her on Tuesday in the hallway. He said students related to the young teacher, who liked to wear jeans and UGG boots just like the students.

Ritzer lived at home with her 20-year-old brother and her sister, a high school senior. The close-knit family was often outside, barbecuing, spending time together and enjoying each other's company, neighbors said.

Mary Duffy has lived next door to the Ritzers in the comfortable, suburban neighborhood in Andover since the family moved there more than two decades ago. She had known Colleen Ritzer from the time she was a baby and said the Ritzers' oldest child had just one ambition in life: to be a high school math teacher.

"All I ever heard is that she loved her job," Duffy said.

Ritzer's uncle Dale Webster provided a brief written statement in which the family asked for privacy.

"At this time, we are mourning the tragic death or our amazing, beautiful daughter and sister," the statement read. "Everyone that knew and loved Colleen knew of her passion for teaching and how she mentored each and every one of her students."

There was no reason to believe anyone else was involved and there was no public safety danger, authorities said.

All public schools in Danvers, about 20 miles north of Boston, were closed Wednesday.

The high school's students were planning a candlelight vigil Wednesday evening.

Ritzer is the second teacher allegedly killed by a student in the U.S. this week. A Sparks, Nev., middle school teacher was allegedly shot by a 12-year-old student on Monday.