AFP reports citing a schools' spokesman.
The boy brought a .22 caliber handgun into class Monday at the West Kearns Elementary School in the Salt Lake City suburb of Kearns, Utah, and allegedly threatened classmates with it before being reported.
"He is alleging that he brought the weapon to protect himself and his friends from a Connecticut-style incident," Granite School District spokesman Ben Horsley told AFP.
The boy was spotted by schoolmates. They alerted a teacher, who "immediately apprehended and took the student into custody and took him to the principal's office," Horsley said.
The gun was found in the boy's backpack in a classroom. It was not loaded, but the boy did have ammunition, although it was unclear if it was for that type of weapon.
Police were called and he was taken into custody. The boy, who cannot be identified because he is a juvenile, has been charged with possession of a deadly weapon on school property and aggravated assault.
"The aggravated assault charge stems from an allegation that he threatened, or waved the weapon in a threatening manner against three (fellow) students," said Horsley.
"That appears to have occurred during lunch recess time, while the kids were out on a soccer field in the area." The boy was not reported until nearly the end of the school day.
In addition to the criminal charges, the boy has been suspended from the school, said the spokesman, voicing gratitude to the students who reported the incident.
"Our kids continue to be the eyes and ears and the mainstay of our security systems in our school," he said. "We have cameras and things like that, but nothing is more effective than kids reporting dangerous behavior."
Meanwhile, police in California said an 18-year-old student had been arraigned for allegedly leaving a bomb threat note in a classroom on the day of the Connecticut shooting.
Christopher Michael Casey is charged with reporting a false bomb threat and faces a maximum of three years in jail for leaving the note Friday at lunchtime on his teacher's desk at Huntington Beach High School, south of Los Angeles.
A secretary found the note and reported it to the principal. Officers from the Huntington Beach Police Department were called in, the suspect arrested and the school searched. No bombs or explosives were found.
The incidents came days after 20-year-old Adam Lanza blasted his way into a school in Newtown, Connecticut and killed 20 young children and six adults with a military-style assault rifle in one of America's worst ever school tragedies.