SANTA FE, Texas — As soon as the alarms went off on Friday morning at Santa Fe High School, students started running outside the school to escape, according to 10th grader Dakota Shrader.

But some didn't know it was a shooting until they got outside.

"Next thing you know, everybody looks and you hear 'boom, boom, boom, and I just ran as fast as I could to the nearest forest so I can hide and I called my mom," Shrader emotionally explained with her mom by her side Friday morning.

WHAT WE KNOW: At least 10 killed when Santa Fe High School student opens fire

During the chaos, Shrader says she was having an asthma attack and said her friend Ryan helped get her out.

The two ran together from their first period class in the history hallway to outside the school.

While teachers tried to coordinate where students should go, that's when everyone started hearing the 'booms,' Shrader described.

"Everybody just starts running, everybody yelling 'run, go, as fast as you can.'"

Federal and local enforcement sources confirmed to KHOU that at least 10 people were killed and 13 more wounded.

Shrader said she saw one of her friends who got shot in the leg while in the school's art hallway.

That friend told her she was shot then "next thing you know, all the art windows are getting shot at, shattered."