A 15-year-old student with no history of disciplinary problems is facing felony gun charges after authorities found a stolen .40-caliber Smith and Wesson semi-automatic pistol in his backpack as he entered the Samuel Fels High School in Northeast Philadelphia's Lawncrest section, police said.

The weapon was "loaded to capacity" with 12 rounds when it was discovered about 7:35 a.m. Monday as the student passed his backpack through a metal detector, prompting a 45-minute lockdown to ensure there was no other threat at the high school on the 5500 block of Langdon Street, said Capt Sekou Kinebrew, a police spokesman.

The arrest was among the latest incidents at schools in the Philadelphia region, where authorities are being vigilant in the aftermath of the Florida school shooting that left 17 dead. In South Jersey, two teenagers, also with no history of serious problems, were charged with making terroristic threats after they allegedly joked that they were going to "shoot up" Delsea Regional High School, authorities said.

While the teens may have used poor judgement, it does not appear that any of them posed an actual threat to others, law enforcement authorities said. The students names are being withheld because they are minors

"These are teenage boys who don't always make good decisions," said Delsea's Superintendent Piera Gravenor, adding that the situation was handled by police. The students – now in the custody of their parents – will not return to school pending a review by district officials, she said.

In Philadelphia, Kinebrew said the ninth-grader said he stole the gun from a car in his neighborhood (it was reported stolen Dec. 18), but he said he did not plan to use it. "He was an otherwise non-problematic student," Kinebrew said.

Charges include two felony counts for illegal possession of a firearm and possession of a firearm on school property. Kinebrew said students should call authorities if they see anything or hear anything suspicious.

On Friday, a student was arrested at Wagner Middle School in West Oak Lane after the principal called authorities about a weapon brought to school that turned out to be a BB gun. It's rare, Kinebrew said, that guns are brought to school, but not surprising given the number of guns in the city.

>> READ MORE: Everyday gun violence must be part of gun control reckoning | Helen Ubiñas

Four handguns and 38 pellet or BB guns were found at Philadelphia schools last year, according to the state's Safe Schools report.

In the Delsea Regional School District, a student overheard two others talking about shooting up the high school, which serves Newfield, Franklin and Elk townships. The student told his parents, who reported it to police on Sunday, said Franklin Lt. Matt Decesari.

"We did get on it right away," Decesari said. One student was approached at his home, the other in school Monday morning. The teens, both 16 and from Franklin, admitted making the comments, but said they were just joking. Decesari said there was no threat to the school, but added: "We're always vigilant when it come to school security. That's a top priority for us."

Gravenor said she was in Florida when the 17 students and staffers were fatally shot at Marjory Stoneman Douglas High School, a massacre that has prompted widespread debate over gun violence and schools. While the students from her school are known as "good students," she said she would rather act with extra caution than treating the matter too lightly.

Staff writer Joseph A. Gambardello contributed to this article.