Minutes after killing their victims in the library, Eric and Dylan returned to the cafeteria to attempt to detonate their propane bombs that failed to go off when planned.
Eric shot at it - nothing. They managed to partially detonate the other, only to have the sprinklers put it out.
Nine minutes later, at 12:06, Eric and Dylan returned to the library and shot themselves, ending the massacre.
Law enforcement still wouldn’t enter the school for hours.
After Columbine, strategies changed regarding school shootings - police now are required to enter immediately, with the number one priority being to neutralize the shooter(s).