A student at the Texas high school where a gunman opened fire Friday morning detailed the terrifying experience on Fox News Channel.

Leila Butler, a 15-year-old sophomore at Santa Fe High School, was sitting in chemistry class when the fire alarm went off.

She said she and her classmates didn't hear gunshots -- since they were on the opposite side of the building from the art class where the shooting occurred -- so they exited the building as if it was a normal fire drill.

Once they got outside, they realized it was not a fire drill and they were instructed by teachers and administrators to run and get as far away from the school as they could.

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"We just had no idea what was happening," Butler said. "We knew immediately when we got outside that it wasn't what we thought it was."

She said they crossed the highway and teachers escorted them behind a business, where they waited and filled out papers to help with headcounts.

After some time, they were formed into lines and directed toward the junior high campus where they could reunite with their families.

At least eight people, most of them students, were killed, according to authorities.

"It's a tragedy," Butler said. "Local areas have been reaching out and we're going to be having vigils. And anyone who needs help and just someone to talk to, Santa Fe's been very uplifting in helping in that sense, that we have someone if we need it."

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