then we heard the screaming. police say pearson wanted revenge because of what police call a confrontation or disagreement. witnesses saw pierson enter the high school carrying a shotgun and making no attempt to hide it. pierson asked other students the whereabouts of a faculty member, accordingly the librarian and head of the debate team. when authorities heard that the student was asking for him, the teacher exited immediately. i found him. he was running military towards the building. i alerted everybody in the building. that s when i heard two big bangs. zbl in addition to the shotgun. authorities found two molotov cocktails inside the school. one was rendered safe. the other was detonated. that s why the deputies found
reporter: police say pierson appears to have been seeking revenge against a specific faculty member because of what police call a confrontation or disagreement. witnesses saw pierson enter arapahoe high school carrying a shotgun. he made no attempt to hide it. i saw him. he was kind of running military towards the building. i alerted everybody in the building, and that s when i heard two big bangs. just boom, pop. reporter: police say pierson asked other students the whereabouts of that faculty member, reportedly the school s librarian, and head of the speech and debate team. when the teacher heard that he that this individual was asking for him, the teacher exited the school immediately. in my opinion, it was the most important tactical decision that could have been made. reporter: in addition to the shotgun, authorities found two molitaf cocktails in the school. the one was rendered safe. the other had been debt made. that s why deputies encounter aid large amount of sm
shotgun, authorities found two molotov cocktails inside the school. one was rendered safe. the other had been detonated. and that s why the deputies encountered a large amount of smoke in the immediate area. that was ignited either immediately, prior to, or during the shots being fired. reporter: as part of the investigation, authorities will be looking at school surveillance video. they are also searching pierson s car, his home, and another home he had access to. the shooting happened just 10 miles from the infamous 1999 columbine high school shooting where eric harris and dylan klebold killed 12 students and one teacher before killing themselves. my husband was a freshman at columbine, so he s freaking out right now. it s bringing back horrible memories of that. yeah, it s just way too close to home. reporter: and just a few minutes ago, authorities opened up the parking lot behind me.
gunman, identified as karl pierson shot one student before turning the gun on himself and taking his own life. it was pretty scary. there were two shots by my classroom. and then we heard the screaming. reporter: police say pierson appears to have been seeking revenge against the specific faculty member, because of what police call a confrontation or disagreement. witnesses saw pierson enter arapahoe high school carrying a shotgun and making no attempt to hide it. i saw him. he was kind of running military towards the building. i i alerted everybody in the building, and that s when i heard two big bangs, just boom, pop. reporter: police say pierson asked other students the whereabouts of a faculty member, and reportedly the school s librarian and head of the speech and debate team. when the teacher heard that this individual was asking for him, the teacher exited the school immediately. in my opinion, it was the most important tactical decision that could have been made. re
immediate area. that was ignited either immediately prior to or during the shots being fired. reporter: as part of the investigation authorities will be looking at school surveillance video. they are also searching pierson s car, his home, and another home that he had access to. the shooting happened just ten miles from the infamous 1999 columbine high school shooting where eric harris and dillon klebold killed 12 students and one teacher before killing themselves. my husband was a freshman at columbine, so he is freaking out right now. it s bringing back horrible memories of that. it s way too close to home. the sheriff does tell us that he believes that some of the training and the changes that they ve made in temz of their law enforcement protocol may have helped save lives. of course, since columbine, that s really been on the radar