The Arapahoe High School shooting in Colorado lasted for only two minutes and left no casualty. However, as police continued the investigation, the authorities have unraveled some shocking twists.

County Sheriff Grayson Robinson, the officer in charged of the case said that the gunman didn't just come to the school to get revenge on his teacher. He was actually has an "evil intent" of killing multiple students.

The officer said that the 18-year old suspect named Karl Pierson fired six shots right at the moment when he entered the Arapahoe campus. Those shots include the one that he used to kill himself. Robinson added that he didn't accidentally shot another student who was trying to pacify him.

"His evil intent was to harm multiple individuals," the officer told the media on Saturday.

According to further investigations, he fired a round of his shotgun in the hallway while wearing backup ammunition around his body. He also had a machete and carried three Molotov cocktails in a backpack. It was revealed that Pierson purchased the gun at a local store on December 6.

Reports said that Pierson got mad with a teacher/librarian who was mentoring a debate/speech team that the suspect was part of. In September, the teacher, whose name was not released, kicked Pierson out of the team, which eventually got the 18-year old suspect really mad.

"I think he (Pierson) really cultivated his speech and argument skills and really thought that was a big part of his identity," said Steve Miles, Pierson as a freshman. "He probably thought it was a pretty crushing blow to get kicked off the debate team."

One of Pierson's victims was Claire Davis, 17, who was shot in the head while hanging out with a friend in the library. She remains in critical condition and a candlelight vigil was held for her, attended by her friends, classmates and relatives.