Why didn't this ohio school shooting witness alert authorities?

I don't really understand why this witness didn't alert teachers or authorities much sooner????

Linked from http://blog.cleveland.com/metro/2007/10/witness_said_school_shooter_lo.html
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SuccessTech Academy sophomore Rasheem Smith, 15, was in a fourth floor bathroom Wednesday when he saw Asa Coon change clothes moments before he went on a shooting rampage.

Coon removed his slacks and a red and gray hooded sweatshirt and put on black jeans and Marilyn Manson concert T-shirt, Smith said.

When Smith saw Coon load a gun, he left but didn't tell a teacher.

"I don't know what I was thinking, he said. "I didn't want him to shoot me."

Fifteen minutes later, Smith was eating lunch in the cafeteria, also on the fourth floor, he heard a loud sound. Yet, Smith, believing it was nothing more than a book slamming on a desk, didn't react.

Then Smith heard someone shout that a student had a gun. Just then Smith saw Asa shoot a teacher.