WESTMORELAND Co. (KDKA) – Derry Area High School and Middle School were evacuated after an explosion in the science lab.

It happened around 11:30 a.m. Wednesday.

A science teacher, 35-year-old Brain Clawson, was injured during a presentation, after a chemical reaction caused an explosion. He was transported to UPMC Mercy Hospital via helicopter.

“When they opened the door, all of this smoke just like came out of the room,” one student said.

Two students sustained minor injuries because of the explosion — one was injured tripping as they were trying to evacuate the building.

One student says Clawson was mixing Potassium Nitrate and sugar — which can ignite.

“He was doing an experiment to demonstrate chemical reactions … it just had a bad reaction and it exploded in his face,” said student Paul Barnhart, whose leg was burned.

Students said during the evacuation, Clawson did not appear to be concerned with his own injuries, but rather with getting students to a safe place. He’s worked for Derry Area School District for seven years.

About 1,700 students and staff were evacuated into the football stadium Wednesday afternoon.

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