At a Pierson College Master’s Tea on Monday, journalist and author Dave Cullen addressed a small audience of fewer than twenty students about the 1999 massacre at Columbine High School in Colorado — and despite the fact that most of the attendees were young children when the shooting took place, audience memebers said the tragic story still struck an emotional chord for them.

Cullen spent ten years researching the murders committed by students Eric Harris and Dylan Klebold on April 20, 1999, in Columbine, an unincorporated town within Littleton, Colo. Cullen, who was living in Denver at the time, drove out to the school that morning to report after hearing about an incident at Columbine High School and stayed overnight to watch the story unfold. In 2009, he published a book, “Columbine,” that sought to answer essential questions about the crime and the killers.

“Why did they do it?” Cullen asked. “Why did two boys walk into a high school one morning and kill people?”

The two killers, Harris and Klebold, killed 14 other students, themselves and one teacher. Twenty-three others were injured, Cullen said, many severely; Harris and Klebold had packed scraps of metal, glass and sawdust into their guns along with bullets. One victim — who survived and was the valedictorian of her graduating class — was shot point-blank in the face, Cullen said.

Since the day of the killings, Cullen said, he has been through two bouts of post-traumatic stress disorder.

“The most unnerving and eery thing was the next morning,” Cullen said. “There was no crying, no emotions, no movement.”

Harris and Klebold planned their attack a year or more in advance, Cullen said, adding that detailed journals, essays and Harris’ personal website provided him with invaluable insight into the teens’ thoughts. While Harris said he hoped to see people running around like burning matchsticks in his journal — the first entry of which was “I hate the f—ing world” — Klebold’s contained several references to love and drawings of hearts, Cullen said, pulling out photocopies of journal pages, sketches and schedules.

Cullen spoke about the aftermath of the event in Columbine, including survivor’s guilt among community members and the recovery of students and adults in the community. He then discussed characteristics belonging to psychopaths and whether Harris and Klebold can be classified as such. The statistically proven indications of psychopathic behaviors in children are cruelty towards animals, a fascination with fire and explosions, and bedwetting, Cullen said, adding that he would describe Klebold as a “depressive” and Harris as a psychopath.

“Know what the treatment is for psychopaths? Nothing,” Cullen said.

The tea lasted nearly two hours, and three students interviewed in the audience said they were fascinated by the talk.

“He’s such a vivid storyteller in the way he presented the psychology of the killers,” Erin Biel ’13 said.

Danielle Trubow ’14 said she got chills thinking about the students and that the talk “hit home.”

Cullen’s spontaneous and tangential speaking style was challenging for one of the students interviewed.

“There were so many questions and so little time; I wish he could have been more concise,” said Albert Chang ’13, a Colorado native who lives less than 15 miles from Columbine High School and who said he had prior knowledge of the shootings. “Still, I liked hearing his firsthand accounts after having my own previous notions.”

“Columbine” is a New York Times best seller and a winner of the 2010 Edgar Award for Best Fact Crime, a literary award granted by the Mystery Writers of America.