The warning that would upend life in Nepal's Tribhuvan Trishuli Secondary School came just after the 9am bell had rung last Wednesday (August 26).
Headmaster Rajendra Dawadi was in the building when he could hear his accountant shouting: "The flood is coming, the flood is coming!"
As teachers began receiving panicked phone calls from relatives, a roaring wave of mud water was already making its way through the valley upstream, swallowing anything in its path and flattening entire towns.
Dawadi and his colleagues realised they may only have minutes to save the lives of hundreds of students. Built in the wake of Nepal's devastating 2015 earthquake that killed nearly 9,000 people, the school had been constructed on a peninsula of sorts, squeezed in between the Trishuli river and a hydropower canal. It was right in the middle of the flood wave's imminent path of destruction.
"We immediately stopped the classes and rang the bell," Dawadi told Reuters in an interview.
The decision saved the lives of more than 900 students and around 60 faculty members, according to Dawadi and other teachers at the school -- a rare glimmer of hope in a natural disaster that killed over 700 people, with more than 3,000 people still missing.
The Tribhuvan Trishuli Secondary School no longer exists. Its former location now sits inside the riverbed.
Headmaster Dawadi was himself once a student in this school, long before he became its headmaster.
"There's an emotional attachment with this school," he said, estimating that two thirds of his life have been spent there.
Dawadi said he instructed buses that were headed to the school with more students to head to safer ground, and quickly began to evacuate the school. As chaos spread, at least one student fainted, Dawadi said.
Parents arrived with motorbikes to pick up their children. Others were brought to safety in buses or ran to higher ground.
By the time the last bus crossed a nearby bridge across the river an estimated 14 minutes later, a wall of water was making its way through the town of 60,000.