The police chief in Murrysville, Pennsylvania, says investigators are checking reports of a threatening phone call Tuesday night between a student and a 16-year-old accused of going on a stabbing rampage the next morning at his high school.

Authorities described the scene of Wednesday's stabbing attack at Franklin Regional High School.

"I can tell you what we saw when we got there was a hallway that was pretty much in chaos, as you can imagine. A lot of evidence of blood on the floors in the hallway," Murrysville Police Chief Thomas Seefeld said. 

He also praised the actions of administrators during the attack.

"The Assistant Principal Sam King did a role that is very admirable. Sam was actually able to tackle the suspect," Seefeld said. 

Seefeld says a school resource officer was also able to get handcuffs on the 16-year-old suspect, Alex Hribal.

One student at Franklin Regional High School says Hribal had "just a blank expression" when he allegedly attacked 21 students and a security guard with two knives. 

Hribal is being described as a shy boy.  

Students at the school say he kept to himself, but was never mean or violent. 

The parents of the suspect are beside themselves and are apologizing to the victims.  

The attorney for the family of Hribal tells ABC News his parents are "devastated," adding they can't figure out why their son carried out the attack.  

Attorney Patrick Thomassey says the sophomore, who was a student at Franklin Regional High School, was a good student who mingled well with others.

His parents say he was not a loner, was never in trouble before and that he worked well with other students.  

Thomassey says he thinks Hribal understands what he did but may not have a full grasp on the fallout.

"At this point, he's confused, scared, depressed," he said. 

Thomassey tells ABC's "Good Morning America" they're still trying to figure out exactly what happened and why. He was asked about Hribal's state of mind.

"I don't think he, at this point, understands the gravity of what he did. I don't think he realizes how severely injured some of these people are," Thomassey said. 

Hribal will be charged as an adult on four counts of attempted homicide, 21 counts of assault and one count of carrying a weapon on school property.

He was denied bail yesterday, as District Attorney John Peck argued he is a threat to the community and himself.  

Hribal will also undergo a mental evaluation to determine if he is fit to stand trial. 

All of the victims are expected to recover.

Classes are cancelled for the next few days as the investigation unfolds and students and staff try to come to grips with the shocking violence many witnessed firsthand.

Meantime, one of the students injured in yesterday's spree is speaking out.

One of his first thoughts after the knife sliced into his back,

"Will I survive, or will I die," said Brett Hurt,

Hurt said his friend helped his life,

"started putting pressure on my wound, making sure I didn't bleed out," he described.

Hurt's mother said,

"so far every parent can be blessed to know that their child is still here, to me that's a God-send."