RIVERSIDE, Mo. - Park Hill South High School was locked down for several hours Wednesday.
Nicole Kirby, the district's director of communication services, said the lockdown came after the school received a threatening phone call.
"The person that called told us something that we took very seriously," Kirby said.
Students in classrooms were locked inside. Those in the cafeteria were rushed to the gym.
"We were just sitting there, and then everyone starts getting up and running to the gym," sophomore Alex Berhenke said.
Students said they sat in the gym for more than an hour before their principal told them why they were there.
"He finally told us that someone made a call, and threats that someone had a gun in the school," freshman Zaine Lindenberg said.
A parent said her daughter text messaged her that some students were being moved from the cafeteria to the gym, and that the school was on lockdown.
The daughter texted her parent, and said if any students had to use the restroom, only four were allowed to go at the same time, and each student would be searched.
The school said students were locked down in various places in the school, as well as the gym.
"My mind is going in so many different directions, because we have seen in other cities that gunmen have entered, and it was bad," parent Zarinah Dawan said as she waited in her car for students to be dismissed, among dozens of other parents.
Many parents said they were hoping for the best as they waited, but scary scenarios were running through their minds.
"Everything, especially worst case scenario. I was absolutely terrified, especially with the recent events. You just can't help but think what if it's real this time," parent Cassandra Keschinger said.
Riverside Police are investigating the incident. They have not yet released what was said during the phone call, or from whom or where the call came.
School officials notified the parents by text message, email and social media about the lockdown.