CONCORD — As classes let out Thursday at Concord-Carlisle Regional High School, classmates defended a 17-year-old student against police allegations that he threatened to use handguns and knives against a small number of classmates, faculty, and the school resource officer.

Some said he had been bullied. Others said his alleged actions had been overblown. And still others maintained he was a student with integrity.

“This wasn’t the type of person he is,’’ said Johnny Hudson, a 17-year-old junior who was on the football team with the student, who was not identified because he’s a juvenile. “This doesn’t change the way we feel about him as a person.’’

Police charged the student with committing a crime against the public peace by threatening to use deadly weapons in a school, and threatening to commit a crime, Concord Police Chief Joseph O’Connor said. The threats were allegedly discovered in the student’s notebook.

The chief said in a statement that police went to the school Wednesday after the principal reported that a student, who had an outburst in a classroom, was “found to have written serious and specific threats against members of the school community in a notebook.’’

Police, who continued Thursday to investigate, said no weapons were found.

Classmates said the student had friends but on occasion was teased.

“If I saw him sad in the locker room, I’d try to cheer him up,’’ Hudson said.

Charles Israel, also a 17-year-old junior, said classmates wanted the student to know that people were speaking up on his behalf. He had a hard time at school, Israel said.

“No one paid attention to how he felt or gave him help,’’ Israel said. “They treated him badly.’’

The youth was arraigned Thursday in Juvenile Court in Framingham, O’Connor said.

“The threats were very disturbing,’’ O’Connor said at a news conference. “They were specific individuals that were specifically named. It was quite clear what his aspirations were.’’

He said those mentioned as possible targets have been informed.

“We believe this is a lone individual,’’ O’Connor said. “We’re not looking for any additional suspects.’’

Police said classes continued Wednesday and Thursday.

Adriana Crosby, 54, of Concord, whoseson is a junior at the school, called the incident unnerving.

“Thankfully, our school is good at being responsible and taking action quickly,’’ Crosby said. “The bottom line is we all have to keep our eyes open.’’

The student was arrested after he gave a staff member a notebook containing messages that threatened the school community, the school system’s superintendent, Diana Rigby, said in an interview. Rigby said the student was taken out of the school, hospitalized, and taken into custody by police.

“The student has been arrested, and he will not return’’ to the high school, Rigby said in a letter to parents. “All involved parties have been notified and informed of the school’s response.’’

“School safety for our students and staff is paramount, and it is always our top priority,’’ Rigby added.

Andy Rosen of the Globe staff and Globe correspondent Andrew Grant contributed to this report. Cristela Guerra can be reached at cristela.guerra@globe.com.