Instead of getting an entire different medication, he got a different brand name and still had the same side effects he was having before (Zero Hour).
The Shooting.
Dylan and Eric had one goal on April 20, 1999; to kill as many people as possible, then to commit suicide after everyone was killed. Though they had this clear objective, they only managed to kill twelve students, one teacher and injure twenty-three students. Dylan and Eric planted two twenty pound propane bombs, which were set to go off at 11:17, which is when most students were in the cafeteria for lunch time (Zero Hour). At first, Eric threw a pipe bomb, but the pipe bomb didn't do much damage. When they noticed there were no results from tossing the pipe bomb, they waited for their propane bombs to detonate. When the propane bombs failed to explode, they began using guns to kill students. The first students who were hit by the bullets were Rachel Scott and Richard Castaldo who were both 17 years old. Rachel later died while Richard was hit with a bullet and paralyzed (Zero Hour). Eric and Dylan proceeded to go inside to begin the killing spree.
Eric began shooting in the hallways while Dylan went to the cafeteria to see why the bombs failed to ignite. When people heard Eric's guns going off, teachers tried to get every student into safety. In the cafeteria, Dylan killed Daniel Rohrbough and injured Sean Graves who were both 15 years of age (Zero Hour). In the hallways, Eric managed to injure Lance Kirklin who was 16, Michael Johnson who was 15, Mark Taylor who was 16 and paralyzed Anne Marie Hochhalter who was 17 at the time. The killing spree didn't stop there. Patti Nielson who was a teacher at Columbine, and a 17 year old student named Brian Anderson were injured by bullets and flying glass. Stephanie Munson who was 17, was shot in the ankle but managed to make it out of the building alive. When Eric was shooting down the hallways, he managed to shoot Dave Sanders, a sports coach and teacher, in the shoulder.