A Bronx school went into lockdown this morning after a campus aide overheard a student talking about his gun — a toy gun it turned out, officials said.

The lockdown was called off after an hour and no weapon was found at PS 4, on Fulton Avenue and East 174th Street, officials said.

A campus aide reported hearing a student say “something about a gun,” a law enforcement source said. School officials didn’t want to take any chances so they closed down campus, as heavily armed police swarmed PS 4 to search for that student.

The 12-year-old boy told police he was talking to a classmate about his toy Nerf gun, which he left at home, law enforcement sources said.

“There was a rumor that a student in one of the schools on the campus came to school with a gun. The principal called a lockdown and police are on the scene,” Department of Education spokeswoman Marge Feinberg said during the lockdown that ended shortly after 9:30 a.m.

Even though it turned out to be a false alarm, parents rushed to campus fearing the worst.

“The worst part is just not knowing anything or getting any answers. My husband, Ed, was running out in the park looking for our daughter,” said Jacklyn Williams, mother of a 9-year-old student at PS 4.

“It’s nerve racking. There are police officers here with assault rifles and there are helicopters flying around. It’s really scary out here.”

Parent Vanessa Sanchez 38, said: “There were so many rumors. I didn’t know what was real. I heard it was a Nerf gun, a fake gun or something like a prank.”

“When I got to the school, it was crazy,” added Sanchez, a mother of a first-grader. “People were yelling and running around. There was a huge group of people in the park across the street. I was really nervous and worried. I didn’t know what happened to my son. I want to make sure he was safe.”

A school official made an announcement to parents outside saying : “The action is over. Your kids are safe and secure. School will resume as normal”.

People are heading back into the school now.

Additional reporting by David K. Li