Alex Hribal, the suspect in the multiple stabbings at the Franklin Regional High School in Murrysville, Pa., is escorted by police to a district magistrate to be arraigned on Wednesday, April 9, 2014, in Export, Pa. Authorities say Hribal has been charged after allegedly stabbing and slashing at least 19 people, including students, in the crowded halls of his suburban Pittsburgh high school Wednesday. (AP Photo/Keith Srakocic)

New details are emerging about a 16-year-old student accused of going on a stabbing spree at a Pennsylvania high school earlier this month.

A criminal complaint obtained by NBC News claims that Alex Hribal told an administrator who tackled him, "My work is not done, I have more people to kill."

The complaint also said the April 9th attack at Franklin Regional Senior High School may have been pre-planned.

A note found after a search warrant was executed on Hribal's locker included a chilling message that could have foreshadowed the attack.

"I can't wait to see the priceless and helpless looks on the faces of the students of one of the 'best schools in Pennsylvania' realize their precious lives are going to be taken by the only one among them that isn't a plebian," the note said.

Hribal faces 21 counts of attempted homicide for the melee that injured 21 people.

Classmates told The Huffington Post that Hribal was a quiet and smart teen who wasn't bullied.

"One of the kids he stabbed was a good friend of his," an 11th grader, whose first name is Santino, told HuffPost. "He didn't have a lot of friends, but he was not bullied."

Hribal was charged as an adult.

"He talked to me and a couple other people, but he was really quiet around other people," said Jake, Hribal's lab partner in biology. "He's really smart."