Livermore police raced to East Avenue Middle School Wednesday afternoon after someone reported seeing a man with a rifle walking through a school hallway.
Officers searched the entire campus and did not find anyone with a gun or any evidence.
East Avenue was closed between Jensen Street and Hillcrest Avenue for about three hours.
The report came in an anonymous phone call just before 5 p.m. The school district said only a handful of teachers and students were still on campus at the time
They said an officer was in a locked room with the students and staff at 5:15 p.m. as police actively searched for the person outside. The school offers an extended daycare. Those students, plus administrative staff were still at work at 5 p.m.
Our news helicopter flew above the school and showed two dozen police cars in and around campus. There were also pairs of officers hugging the corner of buildings armed with guns searching for the man.
Police said 25 officers were making a room to room sweep of the campus.
Many parents gathered outside the police perimeter, anxiously waiting for their children to be released. One mother talked via cell phone with her sixth grader who was inside during the lock down. Her daughter told her that she was fine and that she was "just twiddling her thumbs."
In the first 90 minutes after the call, police were unable to find any signs of a gunman. The school remained on lock down under an abundance of caution, according to school officials.
NBC reporter Bob Redell sent the below photo from the scene.