Three meteorology students died in a car crash while returning from a storm-chasing trip in Kansas.
Nicholas Nair, 20, Gavin Short, 19, and Drake Brooks, 22 – from the University of Oklahoma – died at the scene.
The collision came just hours after Mr Nair and Mr Short posted videos on Twitter from Herington, Kansas, of a tornado passing over a highway.
Driving back to Oklahoma in stormy weather, their vehicle hydroplaned and was struck by a tractor-trailer.
They had been travelling southbound in Tonkawa, Oklahoma – just over the Kansas border – when the accident happened.
Their Volkswagen Tiguan skidded on the water, became stuck in the outside lane of traffic, and was then hit, according to Oklahoma Highway Patrol.
The driver of the tractor-trailer has been released from hospital.
“Drake, Nic and Gavin were united in a shared passion,” University of Oklahoma president Joseph Harroz, Jr said in a statement on Sunday.
“As we grieve this immeasurable and profound loss, we also remember the root of their chosen calling, which was to help others.
“Their pursuit of that calling is admirable and serves as an inspiration to all.”
The three students were reportedly part of a wider group of University of Oklahoma students who travelled to Kansas to chase the tornado over the weekend.
Storm chasing involves tracking and following a tornado or hurricane, often collecting photos, videos and records of weather conditions.
Some storm chasers do it for research or for media coverage, and others for the thrill alone.
On Saturday evening, the National Weather Service in Norman, Oklahoma posted a video on Twitter showing a weather balloon with the students’ names on it.
“On this very sad day in the Norman weather community, our evening weather balloon launch is dedicated to Nic, Drake and Gavin,” the service said.