Pa. High School Stabbing Reveals Assailant's 'Anger' and 'Disorganization,' Expert Says

April 9, 2014— -- A killer who chooses a knife as a weapon has a sociopathic personality that reveals deep-seated anger, a criminal justice expert said in the aftermath of the mass stabbings today at Franklin Regional High School in Murrysville, Pa.

A 16-year-old armed with two knives allegedly injured 20 people aged 15 to 60 in a stabbing and slashing spree inside the school before he was tackled by the assistant principal, according to authorities.

Four have injuries described as "serious" wounds to extremities and were flown to area hospitals for treatment. No fatalities were reported.

Others were not actually stabbed, authorities said, and some of their injuries were cuts and scrapes.

"This is what we call a disorganized homicide attempt," said Herb Nieburg, associate professor of law and justice at Mitchell College in Connecticut. "Someone who uses a knife is extremely angry and very out of control. It indicates they really wanted to inflict pain –- it's not as quick as a gun."

Stabbing crimes don't make headlines as often, but historically there have been two notorious acts, according to Nieburg: serial killer Jeffrey Dahmer and accused axe-murderer Lizzy Borden.

Dahmer was convicted of the rape, murder and dismemberment of 17 men and boys between 1978 and 1991. In 1994, Dahmer bludgeoned an inmate to death at the Columbia Correctional Institution in Portage, Wisc., while they were on a work detail together.

Borden was arrested and tried, but eventually exonerated for the 1892 axe murders of her father and stepmother, because testimony provided by others proved inconclusive.

Stabbings are "well thought out and somewhat impulsive," said Nieburg. "But the word that comes to mind is crazed. It's repetitive and they are really out of control. A gun is very deliberate: You take aim and fire. With a knife, it's very deliberate but very disorganized."

Nieburg said there is a "high correlation" of mental illness with an assailant who carries out multiple stabbings.

One of the students at Franklin Regional High School told ABC News that a student pulled a fire alarm during the stabbing.

"[He] knew what was happening ... and he wanted the people to get out," said student Alyssa Finch.

The alleged stabber is in police custody but the identity has not yet been released. Classes at the high school were cancelled today.