Police say a teacher was arrested Wednesday morning after he was seen carrying a gun into Newtown Middle School.

School personnel told police that school security officers had detained 46-year-old Jason Adams after 9 a.m.

Police say they arrived at the school, interviewed witnesses and then arrested Adams. They say Adams had a valid pistol permit, but guns are not allowed on school grounds.

No one at the school was hurt.

For many, the incident brought back painful memories of the shooting at Sandy Hook Elementary School more than three years ago. Twenty first-graders and six educators were fatally shot at Sandy Hook Elementary School in December 2012.

"We don't believe and I'm confident there was no concern for the safety of the personnel in the school," says Newtown Police Chief James Viadero.

Police say Adams has been put on administrative leave, pending an investigation.

Police also say Adams' court appearance is set for April 20.