The second to last scene of the movie shows the boys arriving at school on May 1 and preparing their plan and weapons in Andre 's car . Andre says that he could never have carried out Zero Day without Cal 's help , a sentiment Cal echoes . They run into the school , armed with three pistols , an M1 carbine , and a 12-gauge pump-action shotgun , all stolen from Andre 's father and cousin . The shooting is shown through the viewpoint of security cameras very similar to Columbine High School massacre 's view . The dialogue is heard via the cellphone of a student who is shot and killed . Shooting at anyone they see , Andre and Cal eventually see law enforcement arriving in force after sixteen minutes of shooting . After arguing over whether to engage the police in gunfire , the pair decide to count to three and shoot themselves
Columbine High School massacre
Columbine High School massacre
Zero Day (film)