An elementary school was evacuated for more than an hour Tuesday morning after a fourth-grader showed up with a hand grenade, authorities said.

The grenade still had the pin in it, but it was later determined to be inactive, school district spokeswoman Julie Thannum said. A bomb squad had been called in to remove it from a classroom.

"The boy wasn't mad at anyone," Cpl. Mike Bedrich of the Southlake Department of Public Safety told the Fort Worth Star-Telegram. "He just thought it would be cool to bring it to school."

Old Union Elementary school's staff and 530 students were moved away from the building while authorities in the Fort Worth suburb investigated, then were allowed to return a little over an hour later.

Thannum declined to say if any action would be taken against the student.