The 16-year-old accused in the Franklin Regional High School knife attack this month wrote on a document found in his locker that he "can't wait to see the priceless and helpless looks on the faces" of his fellow students - and told a school official moments after the stabbing that he had "more people to kill," police said in court documents released today.

Alex Hribal is now charged with 21 counts of attempted homicide and 21 counts of aggravated assault. He was arraigned on the new charges Friday by video conference from the Westmoreland County juvenile-detention center, where he has been held since the April 9 incident at the Murrysville school.

He previously had been charged with four counts of attempted homicide and 21 counts of aggravated assault.

His attorney, Patrick Thomassey, did not immediately return a message seeking a comment.

In a criminal complaint detailing the new charges, police wrote that, after vice principal Sam King tackled him, Alex would not drop the two 8-inch kitchen knives he brought from home to carry out the attack.

"The accused refused to drop the knives and was saying: 'No, I am not dropping them, my work is not done, I have more people to kill,' " Murrysville police Sgt. Charles Tappe and Westmoreland County Detective Robert W. Weaver wrote in the complaint.

While executing a search warrant April 9, police found a document in Alex's locker, dated April 6 and signed by him, that reads: "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 plebeian," investigators wrote in the complaint.

Alex is accused of stabbing or slashing 20 students and a security guard before classes started the morning of April 9.

Two students injured in the attack remain hospitalized at Forbes Hospital: Greg Keener, 15, a sophomore, who is in critical condition in intensive care, and Connor Warwick, 16, also a sophomore, who is in fair condition.

Released Wednesday from separate hospitals were junior Jared Boger, 17, who underwent four surgeries and was among the most severely wounded, and junior Derek Jones, 17.