According to NBC News, Arapahoe County Sheriff Grayson Robinson said Pierson, 18, began the day normally, giving '“gave no indication that anything was amiss." Pierson ate breakfast and then went bowling alone before heading to the school.
The two gunmen in the 1999 Columbine High School shooting in Colorado reportedly attended a bowling class before the attack, but investigators later determined they actually hadn't attended the class. Robinson said there was no evidence Pierson was inspired by Columbine.
The student shot by Pierson, fellow senior Claire Davis, 17, died Dec. 21.