What was the columbine high school shooting?

Occurred on April 20th, 1999 in the state of Colorado. Two popular male students murdered 12 people and one teacher and wounding over 20. 

April 20. 1999 in Colorado Erik Harris & Dylan Klebold went into the school at 11:19am, they'd set up a bomb to go off at 11:14 to distract law enforcement so as they could carry out the massacre, and began to shoot people in the cafeteria. At 11:22 the police responded to the 911 call. 11:29-11:36 they went to the library and began shooting people. At 11:35 the massacre was over having killed 13, and wounded 24( 21 by gunfire). At 12:08 the two counted to 3 & shot themselves in the head, committing Suicide.
The reasons sighted for this were because the two boys were being bullied, members of the football team had sprayed them w/ketchup & mustard and called them derogatory names. They were NOT popular. Video games, music, Goth-culture all were used as a maybe as to why it happened.

What i think is that it adds loudness for preachers/church choirs. it is also able to hold up a lot of weight without pillars. : )) idek tho